Ah, the epitome of teenagers, knows everything and is an expert in things he hasn't been doing long.
Back on topic, OP.
Depends on what you want out of the tank, if you are looking for some aggressiveness in the tank, then bail on the geos, severums, and salvini and go for the jags, festae, jacks, GT, Oscars. Geos and severums are more peaceful but can typically handle themselves just fine, but they don't get big and I could see some issues in the future with a 16-18" Jag picking on them, as well if you ended up with a male festae.
Personally, I would do a Geo only or a Geo/Severum tank, but I am partial to Geos. You could have a very nice setup with some Geos, nice dither fish, etc. G. Abalios, G. Dicrozoster are nice, as Logi mentioned, Red Head Tapajos are also nice. You could always do altifrons, etc. Jurupari are nice, but I wouldn't do a large group of them. You could also look into heckelii, but I wouldn't do a group of them, I would only put one in.
I personally have Abalios and Dicrozosters and like them a great deal. If you have done the large, aggressive cichlids before, then a Geo tank is a nice change of pace. Nice not having to worry about fish beating each other up, they also do a pretty good job of keeping a tidy tank.
With that being said, make sure you are prepared to have a sandy substrate, as Geos dig and sift all day (hence the name). I wouldn't do a thick layer, just enough for them to dig around in.
There shouldn't be any issues with you deciding on groupings and getting 2-6 of each, assuming you pick juvies, if you decide on Geos I would get whatever groups make you happy and keep them. A 260 gallon tank will be fine for a good amount of time while you decide which candidates you'd like to keep and let the attitudes come out of the fish.
I see you have a "4ft sump" but what type of sump are you going to be running?