cpu:gpu is the biggest thing. You need to keep these two as similar to one another as far as speed/quality as you can. This in turn will most likely require a bare minimum mobo, which usually dictates the Ram. Again, the cpu:gpu is the biggest, and as long as you have 4GB + of DDR3 1333 RAM, you aren't missing anything there. Just make sure you compare cpu performance with your gpu performance, as one or the other may hinder its partner.
Best AMD cpu for the price is probably the 955BE or 965 BE depending on OC'ing ambitions. If you are going intel, the i5 is plenty for the sli cards listed next, or an i7 would be the best bang for your buck with the higher 500s.I would recommend either a SLI of 460's or 560's, or a single 570 card or higher (580's are very nice!!!) If you are going AMD, do not go below a 6850...im a gpu snob, so sorry for the biased answer.
Hope this helps with my suggestions. Best of luck, and remember, it's ultimately your decision! Have fun with it.