i can't get my head round it, im building a computer for my mate at the budget of £400, or $650.
Not sure which cpu, i prefer amd. It seams like fx-6100 is pretty good value but for just a little more i could get fx-8120 or there are the phenoms, and intes even, and then there is new amd cpu's coming out.
I have about 2 months, so when the piledrivers come out the current fx's might go down in price
He is going to be mostly gaming and sometimes run a few virtual machines.
AMD is usually good when you need many processing threads.
But games rarely use more than two or three fast cores, making the amd cpu's not particularly suited for gaming.
The 8 thread fx-8120 is actually not as good as the older Phenom II x4 chips.
The new amd trinity cpu's have much better integrated graphics. If a gamer is satisfied with such graphics, then the A10 5800K may be a good choice. Otherwise, an Intel cpu with faster cores will be better if one will be using a graphics card of over $100 or so.
Regardless, it is a bit premature to be making any decisions.
Make up a budget now, and see what prices are when you are ready to buy.
For what it is worth, budget twice as much for your graphics card as for your cpu if you are a gamer.