Best system choice?

Hi. I'm looking to buy a new workstation to handle complexFEA and large assemblies that my current machine simply canthandle. Im running a C2D E6600 with 2GB RAM and a Quadro FX1500.

Ive been quoted for a system incorporating a single AMD Opteron cpuon a Tyan Thunder S2915A mobo, with 8Gb PC2-5300 RAM, Quadro FX1700and XP64.

I also have a quote for an Intel QX9650 on an Asus P5Q WS mobo,with 8GB PC2-8500 RAM and again, an FX1700 gfx card but runningVista business 64.

Which of the two similarly priced machines would you recommend I gofor?

Cheers.SolidworksAdministration