Great system. Really like the cpu. couple suggestions, if you are going to get a GTX 260 you must get the GTX 260 core 216. thats the only one that can compete with ati's 4870. for ram OCZ, Corsair,Mushkin,G.skill, are some good brands. for a hard drive Seagate, and Western Digital are the two best bets.
iv had a look at some comparison tests and the difference between the 260GTX and the 4870 is almost none existant. so i was now thinking of going Cross fire with x2 4870 but, iv always been an nvidia man. i dont know many good ATi card makes, or a good crossfire mobo.
the p5q deluxe has 3 PCI x16 slots(3-way crossfire-able) and the p5q pro only has two x16 slots. i would probably stick with the cheaper one, as they should perform the same. good brands for ati cards include: VisionTech, Sapphire, and some of the MSI's. you basically want a dual slot cooler with the 4870, as they run a little hot. this one has good reviews: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Due to that one you linked aving an HDMI port it cost a lot more. i went for a 1GB none OCed version had great reviews playing crysis at very high with AA etc. so having 2 of them should work out well. thanks for your help! im glad i posted on here.