As far as the pH goes the best pH is a stable one. If your LFS is near you it most likely has the same pH you do. Unless you ae wanting to breed the fish, I would'nt alter your pH. There's plenty of nice centerpiece fish for a community tank. You'll need to decide what you like it's your tank. IMO, you could have a pair of apistos OR Kribs OR the Dwarf Flags. If you want a severum I'd just add one. Theres quite a few other that would work too.