Is that L x W x H?
For angels the deeper the tank the better, if that is 25" tall, not bad at all IMO. Good length and decent depth. Go with the 46 bowfront(36 x 15 x 20) or 75g (48 x 18 x 20) if you can. Although you do sacrifice a bit of height for more depth and length(that's swimming and territory room) but bigger is always better.
I have a 48x12x20 for my tanganyikan biotope (largest fish is cyprichromis @ 6"), I wish I had a 75. These 2" L.ornatipinnis claim a 1'x1-2' territory when spawning. Moving them out of a 29g to a larger tank has helped to bring out their personality. I guess what I'm trying to say is that you put a fish in a medium sized tank (45-75g generally medium-small for something 6" highly dependent on species) lightly-medium stocking and appropriate cover and you begin to see a whole new animal. Like a pair of altums(not WC), 15 BPT or other scooling tetra, a few L104, 12 corys, dwarf being best and as many amazon swords as you can pack in there for a 75 is my idea of a perfect tank for angels.