First off my rig:
Nvidia GTX 285
Thanks a ton in advance
Best advice I can give you is to run the rpcminer-cuda thats included with guiminer (its in the custom miner folder named puddinpop)
Just for comparison:
Opencl mining client with my geforce 460gtx peak at around 72mhash/s
Cuda mining client with my geforce 460gtx at exact same core/memory run at 88mhash/s