These statics are a little dated when the Gigabyte 7950 version 1 was selling for $300 with the AMD game packages since then have come out some interesting 7800 series that give pause at price point and muscle.
Edit: (Comparing of DC & sellable as gaming GPU) Galaxy 660 TI with 3 GB DDR5 (not 2 GB) at the time was about $329. (Memory overclock and runable in SLI mode)
I had 2 of each, 4 total.
If the project accepts multi threads of Open CL then you want a beast of a machine the more threads the better up to a 3770K and it use to be at the high end the most bang for the buck was two of the $300 GV-R795WF3-3GD VERSION 1 which is no longer sold. Made by Gigabyte.
Now that's a lot of money but I completed 1% of WCG Cancer program which means GPU "hauls ass" the 6 year program which included a lot of manual ground work of robotic machines forming 300 million samples was completed in less than 8 month when GPU programming evolved in steps and you had an some type of exponentiation growth of AMD GPU of all levels joining. The Gigabyte version 1 card in Open CL could be o/c to 1200 MHz at stock voltage and some people went to 1250 MHz with upping the voltage. The myth that lowering the memory clock to 950 would make it run cooler never was true.
Now in single thread Open CL it's nice to have a faster processor but few cores/threads keeps costs down since you only need one core for the GPU. Memory speed of 2133 is max though not necessary but this matters more on Nvidia GPU's.
Nvidia GPU's like fast memory with the processor though the cpu cores are not important because only part of a core/thread drives the GPU. Nvidia is roughly 1/4 the speed of Open CL ATI so don't run Nvidia on Open CL.
Back From being very busy. Right now I'm studying for CCNA. Then after that to school for Network Administrator are the present plans.