My gaming desktop right now is actually an old Dell Precision tower with a third gen i7 that I got for $140 off eBay. I swapped out the PSU, upped the ram to 16gb, added an SSD I had laying around, and replaced the Quadro GPU with a 1060. In all it cost me about $350 and comfortably runs every game I own. Power draw isn't too much of a concern since it isn't used too often.