Thanks Jakezori and AfroCichlid! I'll have to read up on the Altifrons and see what I think.
In answer to your question about water, my tap water has a pH of about 6.8 and has zero hardness (it's essentially rain water). I know a lot of people in my area keep discus because we have great water for it (some places nearby the tap water comes out as low 5.5 pH). Unfortunately Angels and Discus aren't quite what I'm looking for right now.
I appreciate the suggestion about the dwarf cichlids, I think that would actually be a really attractive setup. I really wanted to go with something larger for the fish since I have the space (90 is the largest tank I've had), so I don't think that's the direction I'll go right now.
I'm pretty sure I'll go with 4 - 5 geos, a school of tetras (or maybe pencilfish), and possibly a catfish of some sort.