Build or just buy a prebuilt PC?

Just checked some computer makers' web sites, I've found out that pre-built PCs are cheaper to buy than buy the components separately and assembly them. For instance, a gaming PC 710G from Gateway.com is priced "only" $2000 equipped with Pentium4 3.2 GHz 800 MHz FB, 1 GB DDR-RAM, 250 GB SATA HD, 19" monitor, 256 MB NVidia GForce 5950G Ultra, SoundBlaster Audigy2, etc.