Most. Entertaining. Read. Ever!
After reading it all and trying to remember every point brought up (not including sarcasm and b*tch*ng, although that was fun) am i correct in assuming you're after something interesting and different, good personality, a touch of aggresion, but not super monster sized just monster sized? And you can only have one tank at a time?
I don't think anyone can really decide what fish you put in your tank or make a stock list apart from you, all we can do is advise you. What one MFKer thinks is a great fish another may not. So, my suggestions/advice would be to try and get the largest tank you can. You say the 150 is available now but it may be more long term beneficial to wait for a 240-300 to appear if you can. 26'x11' room sounds like a good sized area, i don't know what other furniture or belongings you have to accommodate in there but with the size of the area a larger than normal tank shouldn't look out of place. Stocking wise, it all depends on the capacity and dimensions of your tank what you can ultimately put in it, i'd seriously look at a 180 as a bare minimum (although you did say earlier that any grow outs could go back to the 1000g in you lfs (seems nuts to me, but then i do get attached to my fish!)) But a higher tank width than 2' will give you much more stocking scope, say 2'6" or 3'.
Until recently i had a Perruno/Marbled Pim Catfish which was very similar to an rtc, just different colouring, not as big, and provided lots of movement and activity during the day with a wonderful personality. Fed the right things from small it never showed any interest in live food. It was 18" when it prematurely died and was still growing slowly but not awear of any much larger than that. (although i'm sure someone can prove me wrong!) It's growth rate was much much slower than the tsn and rtcxtsn it lived with.
I do have a Lima Shovel Nose, it is out and active during the day, but tbh i do find it a little dull and boring. Just doesn't have the same personality as other large cats.
An ARTC (Asian Red Tailed Catfish) might work if you're feeling lucky. I think their maximum size is around 24" however they do have a lot of aggression and from what i've read you won't be able to keep other catfish or bottom dwellers with one but should be ok with fish at other levels of the tank if you have a well behaved one. Very trial and error between different individuals.
If you get a wide enough tank then you could try an Aro. Jardini are one of (if not the) the smallest species and probably won't go far beyond 24" but as was pointed out they do have anger management problems. If you lucked in to at least a 3' wide tank then a Silver Arowana would probably be happy there for a long while although could potentially grow longer than the tank is wide. Black Arowana are very similar to the Silver in shape (just a different colour.....bet you can't guess what that is!) but don't grow as quickly or as large and don't suffer drop eye. They are quite rare and expensive if cost is an issue but still cheaper than asians over here anyway.
You mentioned having something small and out of place too. I have/ended up with a 5" Red Tailed Black Shark that i never really wanted (long story) which has the aggression to hold his own with larger fish and not be eaten despite feeders that have been eaten being a similar size to him. It does look very 'out of place' seeing this 5" 'monster' survive with 18"+ catfish, pacu, and even a Dovii!
Hope that was of some kind of help, can't think what else to suggest right now, i normally just walk around my lfs and see what they've got and what might work at the right size!

After reading it all and trying to remember every point brought up (not including sarcasm and b*tch*ng, although that was fun) am i correct in assuming you're after something interesting and different, good personality, a touch of aggresion, but not super monster sized just monster sized? And you can only have one tank at a time?
I don't think anyone can really decide what fish you put in your tank or make a stock list apart from you, all we can do is advise you. What one MFKer thinks is a great fish another may not. So, my suggestions/advice would be to try and get the largest tank you can. You say the 150 is available now but it may be more long term beneficial to wait for a 240-300 to appear if you can. 26'x11' room sounds like a good sized area, i don't know what other furniture or belongings you have to accommodate in there but with the size of the area a larger than normal tank shouldn't look out of place. Stocking wise, it all depends on the capacity and dimensions of your tank what you can ultimately put in it, i'd seriously look at a 180 as a bare minimum (although you did say earlier that any grow outs could go back to the 1000g in you lfs (seems nuts to me, but then i do get attached to my fish!)) But a higher tank width than 2' will give you much more stocking scope, say 2'6" or 3'.
Until recently i had a Perruno/Marbled Pim Catfish which was very similar to an rtc, just different colouring, not as big, and provided lots of movement and activity during the day with a wonderful personality. Fed the right things from small it never showed any interest in live food. It was 18" when it prematurely died and was still growing slowly but not awear of any much larger than that. (although i'm sure someone can prove me wrong!) It's growth rate was much much slower than the tsn and rtcxtsn it lived with.
I do have a Lima Shovel Nose, it is out and active during the day, but tbh i do find it a little dull and boring. Just doesn't have the same personality as other large cats.
An ARTC (Asian Red Tailed Catfish) might work if you're feeling lucky. I think their maximum size is around 24" however they do have a lot of aggression and from what i've read you won't be able to keep other catfish or bottom dwellers with one but should be ok with fish at other levels of the tank if you have a well behaved one. Very trial and error between different individuals.
If you get a wide enough tank then you could try an Aro. Jardini are one of (if not the) the smallest species and probably won't go far beyond 24" but as was pointed out they do have anger management problems. If you lucked in to at least a 3' wide tank then a Silver Arowana would probably be happy there for a long while although could potentially grow longer than the tank is wide. Black Arowana are very similar to the Silver in shape (just a different colour.....bet you can't guess what that is!) but don't grow as quickly or as large and don't suffer drop eye. They are quite rare and expensive if cost is an issue but still cheaper than asians over here anyway.
You mentioned having something small and out of place too. I have/ended up with a 5" Red Tailed Black Shark that i never really wanted (long story) which has the aggression to hold his own with larger fish and not be eaten despite feeders that have been eaten being a similar size to him. It does look very 'out of place' seeing this 5" 'monster' survive with 18"+ catfish, pacu, and even a Dovii!
Hope that was of some kind of help, can't think what else to suggest right now, i normally just walk around my lfs and see what they've got and what might work at the right size!
Hey guys . . . Let's let this thread DIE!!! I think it's gone but it returns . . . It's like a having your home infested with mice or roaches . . . You set traps and lay down poison and they keep coming back.