Hey guys. Got a new cichlid a few days ago and I was wondering what species he was..

I'm going to go pick up about 6 more cichlids for my 40 gallon tank tomorrow. I'm going to turn it into a strictly cichlid tank.
Will mixing them work?
Also, could I get away with 6-8 convicts? Could I just move a 'pair' to my 10 gallon tank to breed them? I'm not worried about the water quality, just agression. I know that by overstocking the tank, I can actually keep it down. That's what I'm trying to do with the 6 cichlids I'm getting tomorrow, or if I hear back from you guys within the next 12 hours, the 8 convicts or so.
Thanks!