I wouldn't buy a pre built computer if I was you, they cut lots of corners, use cheap hard drives, ect.....
If you don't want the hassle of building one yourself then ask a couple computer stores(or if you see a geek walking around frys) how much they'd charge you for assembling parts that you bought, and installing windows/drivers and all that shi t. Think low 100 range. Then you can get a computer thats recommended to you by...... well start a new thread asking for recommendations.
You should be happy with the comp aspire.comptech designed, except that motherboard is pci-e, and the video card is agp.... sooo maybe this video card instead
you could go with something cheaper, but this is about as low as I'd go.
It would be nice to have a sata dvd drive but those are still few and far between.