The NB/Mosfet cooling on the P5Q Pro sucks. The regular P5Q with the little yellow flared pieces has more adequate cooling, larger NB and individual pieces on BOTH rows of mosfets. Neither one of them will overheat or anything, but Its still a stupid decision to cool one row of mosfets but not the other, espically on a top tier board.
I am OCing a Q6600 at 3.0 using P5Q - works great. P45 is great performance/$$$$. Some will say dont use P45 for crossfire. I think it is a great choice for the OP's single 4850 using PCIe 2.0 -X16 slot. But this chipset does support from 1 - 4, X8 depending on the MB make and model and this produces crossfire benchmarks at 1680 X 1050 that is within 5 percent of X48 chipsets. I think you win with P5Q no matter how you run.
My question is not about whether to go P45 or not, but P5Q or P5Q-Pro.
And how do they compare with the MSI X48C Platinum? I have 2x 2GB DDR2 800. And does the DDR3 RAM used by X48 the same as that used by X58? Or are they dual channel and triple channel (incompatible with each other)?
The answer is: it all depends on what YOU want/need from a mobo. Jthorn is happy with p5q, Im happy with pro version, and Im pretty sure that whichever you pick you also will be happy with. And ddr3 is ddr3, its a standard so they are the same just speeds will vary.