I totally understand it's a matter of person taste and after 30+ years of being in the hobby I've kept about everything out there at one time or another. I think that is part of the issue in that I got this large tank and now I have a hard time deciding on one fish or group to keep. I got rid of the community I just had because it just didn't "have my interest" anymore by watching them not really do much but sit there in the 350 tank. Maybe that is part of the issue in that they had so much room that they didn't have to chase, run, chase, run from others and they each had their own space and were happy.
I love the blues on the gorilla blue umbee's and I think that is what draws me to them, however like "ahud" said, having just a couple of fish in such a large tank just seems like a waste of such a large tank. I even thought about getting an MBU puffer with some other fish...however I want to make the right decision so that I actually keep them this time instead of swapping fish every few months because i'm bored with the current stock. That is why I was thinking a species tank to maybe see some breeding and natural habits from the fish.
Sorry about all the typing, but thinking out loud (or by typing lol) and really want to make the right decision this time. I think I need something that is bigger from the start or grows at a faster rate, because the severums were growing as fast a turtle moves in mud....