If you have the money and want to have the best performance, go with core i7. but if you want to support or you're an AMD fanboy, go with AMD.
If you choose AMD, you should change the graphics to ATI 4890 or 4870 1GB. Later on, you have the option to add another one in (CFX).
If you stay with GTX 275, change the mb to 790GX. Reason ppl get 790FX is to run their 2 ati gpu x16-x16.
Make sure you get a great psu, any corsair, pc power & cooling & antec 750w power supply is great.
Last thing, get an aftermarket cpu cooler...