Rosewill generally makes PSUs that aren't very good. You could try for a lower wattage Corsair, say the 650TX instead of the 750W version. Actually for most uses something like the 450VX should be plenty.
Corsair is the best quality of these. I would definitely get that. Do NOT get the Rosewill. It is crappy quality and could fry and take out your system. The other three you've listed are ok quality, but I wouldn't get them unless they were much cheaper than the Corsair.
Asus P5Q Pro Motherboard
2x sata seagate HD 500GB
2x2gb - 4GB DDR2 800 OCZ memory
Q6600 quad core
4870 visiontek ATI video (not planning crossfire)
2x sata DVD-RW
PCI wifi card
(maybe a TV turner in the future)
The 4870 says minimum of 500w supply. the 650w Corsair is the same price as the 750w with special price. the 550w corsair is $65 but is that pushing it?
Is paying an extra $40 from the OCZ and Cooler master worth paying for the Corsair one?
Yeah, I'd pay the extra $40. The 650TX is powerful enough for what you got there, but if the 750TX is the same price get the 750TX. Your PC will not consume more just because the "maximum wattage the PSU can deliver reliably" is 100W more. You just get more room for future upgrades, that's all.
I'll throw my opinion in the hat too. I went with a Corsair TX750 as well due to the reviews and recommendations I got. Last month I had an Antec 550W fail and take out an entire P4 670 system. People don't realize how important a good power supply is...and not just the voltage.