unpopular
Been spending a lot of time on here!
It tools some hunting but I found what I believe to be reliable information talking about the AMD like you mentioned. I don't think I need a $10,000 machine and believe their base Mac Pro or intermediate version should surface. That combined with a good high res monitor should work.
I really do not think that my modest K2000 though is the reason my Photoshop numbers aren't as impressive as I'd expected. I think this is because my clock is running at 2.7ghz/core - even with 12 cores and 24 threads, Photoshop just doesn't seem to utilize them.
That isn't to say Photoshop performance is lacking, and I have never once felt that it got in my way. Benchmark-wise though, Photoshop doesn't perform as well as I've come to expect from applications that do utilize multiple cores efficiently. But again, actually using Photoshop I've never noticed a problem.
It may be that Nvidia cards are just not as well equipped for OpenCL as AMD cards are (a pretty well known fact, and one major reason I'm thinking of switching), but I still feel like Photoshop is more processor intensive than it's implementation of GPGPU.
If you're really looking into a workstation, again, the Dell T-series has been great and the HP Z-series, albeit a bit more expensive, likewise looks promising. And I do recommend workstations. Consumer PCs are, for the most part, total garbage.
I got mine from these guys: Dell PowerEdge Servers HP Proliant Servers Xeon Processors