Share 'Desktop Help Please'

My kid's b-day is coming up he'll be 12. My wife and I are going to get him a desktop to replace his laptop (that's going to me for capture and guiding-so this is important lol). He's a gamehead and of course he wants these unbelievable graphic cards ($$$) and that's not happening w/a budget of around $600. Since I'm not up on gaming needs/requirements, I was hoping some of you more computer savv…