Yeah, under about $700 you are going to be in need of an upgrade in the near future, or just have to live with lower graphics and resolutions (which really look bad if you are dropping under the monitor/TVs native res) A good CPU and GPU will run half of the $500.
Haven't been part of this conversation but, AMD over Intel (processor). Gaming, AMD cheap no graphic support, Intel, expensive with graphic support. That's where your money is, graphic support and memory. You can build a unit for under $1000 that will last as a gaming CPU for 5 years with AMD. $700, 2 to 3 years and anything less is a waste of time. If you decide to build cheap, research the parts and make sure they will meet today's ultimate numbers so you can upgrade for at least the smallest amount of cash. AMD and a good graphics card. I built an AMD 6 core for my son and it crushes all frame rates, and I built this in 2011.