Depending on the algorithm I was mining I used different clock mhz because higher didn't always yield more kh/s.

+135-170 mhz core
+500-650 mhz mem

Scrypt ~280-290kh/s
Scrypt-Jane N-14 (Yacoin) ~3.3-3.5kh/s
Scrypt-Jane N-11 (Cach) ~480kh/s
Scrypt-N (Vert) ~145kh/s
HVC 10500kh/s
Fugue 94000-97000kh/s
Groestl 3150kh/s

Beyond just hashrates, different algorithms had different energy consumptions levels too. Scrypt being the highest consumption offender for lowest payout.
Yac is great. 8x cards on two machines only pulled 600w from the wall. Fug = 505w, Scrypt and ScryptN = 700w.