First of all, I assume you're using the default Phatk kernel in CGMiner.  Switch to Diablo.

When you say "I will not mine past 12," I don't get what you're saying.  12 intensity?  Mine anywhere from 9-14 with these.  I mine at 9 on two Gigabyte 7870OCs, and 14 on an MSI 7870.  

I get about 460Mhash on all 3.

2x Gigabyte:
Vcore = 1.275
Fan = 85%
Engine = 1220Mhz
Memory = 625Mhz
Intensity = 9
Kernel = Diablo

1x MSI:
Vcore = 1.275
Fan = 85%
Engine = 1240Mhz
memory = 625Mhz
Intensity = 14
Kernel = Diablo