I would say future upgradability would be of major importance. Go ahead and get a decent gamer for under $1000 (if that's your limit right now), then throw cash at it in smaller chunks later on. I recently bought a Cyberpower desktop (you can see my post in this forum), and I am very happy with its performance, so you've got a recommendation from me for that company. Their prices are very good. I would get at least the intel i5 quad-core processor (I notice most have a free upgrade to faster i5's, and i7 would be even better) and a video card with at least 1 gig of memory, preferably more. Ram is really cheap right now, so get at least 8 gigs. Remember, you're going to have to buy a monitor, keyboard and mouse as well if you're replacing a laptop. They did include a mouse and keyboard for free, but both are in my closet for emergency back-ups (cheapo's), but they would work until you could upgrade those as well down the line. A 19 inch wide-screen monitor can be had pretty cheap these days. Hell, I got a 27" Asus for $299, and it looks great! Might want to call or email them and ask what processors the MB your thinking about will support for future upgrades. I'm not sure about the diffent sockets. Have to ask Roland about that. But adding more Ram and more powerful video cards in the future won't be a problem. The rest of the stuff like the case, optical drive, hard drive size etc is personal preference. A new system with roughly these stats would keep you gaming happily for quite awhile. Be sure to post your stats here so we can see what you got! Good luck!
This one seems fine to me, and if you order on or before April 2nd, they have some great free upgrades during their March Madness sale! Check the upgrades out on the top right of the page. They also highlight the deals down the upgrade lists. $709!http://www.cyberpowerpc.com/system/Gamer_Xtreme_2200/
Edit: Ok, now they have Easter specials going on. Worth looking into!