Looks ok, but I would just get a plain 4870, with that motherboard if it really isn't enough power which I doubt add in another and crossfire it.
For me I would go with the Q6600 but its your choice, I personally think the Q6600 is better in terms of keeping the system future proofed than the dual core, and trust me a Q6600 will handle anything you throw at it game wise so its not going to be a bottleneck and it does overclock very easily if you need more power.
PSU wise the big rule is stick with a trusted brand: I like Hiper for slightly cheaper but still good high performance PSUs but it can be hard to get the better models. Antec is a good all rounder I have an 850W Quattro and its a very nice modular power supply but Enermax, Tagan, Akasa also put out good value quality supplies. My 850W is possibly high for my system(you can look in my profile to compare with yours) it would have ran on a 600W just fine but I wanted more breathing space and 850W should last a good long while and the racing stripes were cool.
Cooling depends on the case, I like Antec cases as they balance the price/features really well and you get the most bang for your buck the cases are also of the highest quality and come with plenty of decent quality Antec fans so you don't need to buy extra usually meaning you just need to worry about CPU cooling.
If you want to overclock get a good CPU cooler, like a thermalright 120 or 90 with a good quiet fan like a Noctua 120mm PWM. If you want to maybe overclock but just want something good and not too expensive the Arctic freezer 64 is fantastic it cools great for not too much money. If you wont be overclocking the HSF you get in the box with the CPU will do just fine, allot of the intel systems use a version of the Arctic Alpine which is a nice cooler.
Edited by warriorscot, 15 September 2008 - 06:58 AM.