I don't know much about computers but if you get a dell or HP(like me) and you're going to upgrade the video card you should make sure that your power supply can handle it. Even the dual core ones usually only come with a 300 watt power supply.

2xM80 VP180 2xQS8 2xM3 HSU STF3 LG 60PS11 Denon 3808 ATI 1506 LCR 2xATI 1502 Oppo BDP-83