Your tank is the same as a 55, except 3 feet long, not 4 feet. I have a 55 with 5 adult koi angels, 2 adult golds, 1 adult silver, and around 15 quarter to half dollar size golds, silvers, & koi, plus a couple of plecs. Had a couple of adult marbles in there, they went to a friend a month ago. Koi are future breeders, the rest are for sale, I like to bring these to club auctions for my buddies.
2 Eheim canisters, an old AC 200, and a home made 230 g.p.h. filter, along with 50% weekly water changes make this work.
Seeing as your tank is 3/4 the size of a 55, 1 or 2 adults will be fine, tank space wise. You just need to worry about compatability. The marbles I got rid of were a pair that didn't produce strong spawns, but would tear the hell out of other angels in a tank. That is why they were in the 55, to spread the aggression. Previously they were in a 65 with 2 adult silvers, 3 adult zebras, and 1 black. They tore up the black so bad, I thought I was going to lose him/her. After a month with some meds & lots of water changes, the black is looking good.
Angels are cichlids, despite their delicate looks. Each has their own personality, and some are more compatable with other angels than others. Seeing as tank space is not your problem, but compatability is, I would go with 4 or 5 smaller ones, trading in some as they get larger.
Tolak