Why in BF3 forum?
And you should define what "mid-cost" means to you. Also how you want your gaming experience. For example...I run a rather "old" Quadcore with 2,4 on each core, 4GB RAM and a Radeon HD6870. I can play BF3 on high settings fluently. Ultra is somewhere around 20-30 FPS, so still KIND OF playable but the difference (visually) is not really big so high is very okay.