I have several SFF Dells with I-5-3470 that I want to convert to gaming PC's, I know I will need new case, what is good 1080 level GPU should I use? Is 8 gigs of DDR3 ram enough, only 2 dim slots sadly. I have 3 budgets. $150,$250 and $350. This is for PSU, case, GPU and more ram if 8 gigs wont work