@ Haydox: Keep with it! Overclockers have improved their service game over the years but can still be 'difficult' at times. I would give good money to see the look on the managers face when he heard of the possibility of County Court action

Did not realise the 5850 was getting so 'cheap'
If I had n't got the 5770 recently (plan on CF for the new build next year-first time for a dual card rig!) one would already be on the way.
Because you use Photoshop a lot and I'm not sure what, if any, GPU accelleration the HD5850 has for it, I would say the GTX275 is going to be your best choice: It's hardly a slow card and is DX10 compliant, and it will be some time before DX10 or even DX9 dies out, so the card should last quite some time.
And did you know the Q6600 is a good overclocker?
😉