Angels. The crack of the aquaria world
LOL They are really addictive; be warned. I currently have 4 angels in my 25 (1 adult, 3 juvies) along with three 2-3" clown loaches and a large plec, but am getting a 55g at the end of the month to accommodate them properly. I wouldn't even have that many, but I keep walking into pet stores
I tend to go by the Angelsplus site for stocking them:
"Nickel size bodies 1 fish per gallon
Quarter size bodies 1 fish per 2 gallons
Silver dollar size bodies 1 fish per 3 gallons
Stock ready to be paired 1 fish per 5 gallons
Full grown breeding pair 20 gallon tall"
This is a GENERAL guide and does not take into account water husbandry and individual fish personality. You can read more here:
http://www.angelsplus.com/care-angel.htm. With good water parameters and tank care, they can easily do well with 10g each, assuming they all get along (another story entirely).
They are really personable, seem to have fairly good memories for creatures with teeny tiny brains (they know the diff between my hubby and I) and are consummate beggers. Domesticated angels are fairly hardy as compared to the wild varieties, and have decent life spans as well (5 yrs seems to be avg with good care).
There are a bunch of angelfish specific forums/websites out there. Between the info you get here, and the stuff you find on those sites, I think you'll have all the info you need to make an informed decision:
http://www.angelsplus.com/care-angel.htm
http://www.aquaworldnet.org/test/
are good places to start.