I have to agree with Megabot. Build your own and you will get a better machine, cheaper than buying a premade one. If you check out
www.hugebee.com they have a section where you can buy a case prosessor, motherboard and powersupply assembled by them , but the rest of the case is empty. All you do then is pick what you want and swap all your old drives and cards into the new frame.Doing it that way cost me only $400 to build my new machine because I didnt have to pay for a ton of things I already had.