Bolivian Ram or Cockatoo Dwarf in 27 Gallon?

[serbusfish]

My planned species list is as follows:

6 Black Skirt Tetras
5 Mountain Cloud Minnows (possibly replaced with 6 Cherry Barbs)
1 Pearl Gourami/Paradise Fish/Betta (depending how tetras react)
2 African Dwarf Frogs
1-3 Filter Shrimp

Now I was thinking of having either a Cockatoo Dwarf Cichlid or a Bolivian Ram. I really like the Cockatoo's but ive heard they require VERY clean water and VERY stable temperature and im worried im going to end up messing this up and killing it, ive heard Bolivian Rams are hardier, but really I dont know much about either or if they will mix with my other species or not? (I only have the minnows and 4 black skirts atm btw).

So basically would either of these Cichlids work in my tank, which would be the better one to go for and could I get just a single male or do I have to get a male and female?