(takes a deep breath)
Pair of Jack Dempsey
Single Green Terror
Pair or a few Firemouths
Pair or a few Convicts
Pair of Salvini
Single Texas
Single Female Midas/Red Devil
Single Grammodes
A few Geo Species
Pike Cichlid
Single Oscar (questionable for life)
Pair or Single Blood Parrot
Single Flowerhorn
A few Dwarf Rams/Apistos
Pair or Single Severum
Few Angelfish
Few Discus (experienced keepers only)
Single or Pair of Nigaragua Cichlid
(and exhales)
That is everything I can think of off hand, though there is more and more rarer choices, but most of those are readily available. As for bottom dwellers, Plecos are popular but do get kind of large, and various "upside down" catfish such as Lace and Featherfin Synodontis species have always worked well for me, and grow quickly and to a nice size for a 55 gallon.
I unfortunately have no experience with Bichirs so I cannot advise you on that, however there is a section on here for it, and I'm sure the forum goers there would have an answer on stocking compatibility.