I have a choice to buy one of these two rather new Dell computers from a reliable source. Please help me weigh out the best option (both are XP SP2 and do not come with monitor)

You'll see that I am basically trying to decide between a Dual Core 3.0Ghz on a 10,000 RPM drive with a second 250GB 7,200 drive for about $400 more than the QUAD core 2.66 Ghz on one single 250GB 7,200 RPM drive. Which configuration is a better (overall faster) developer and and basic power-user stuff (i.e. VFP, Office, Visual Studio 2008? I do not care about the $400, I just want the overall best machine. For some reason the DUAL Core 3.0 Ghz on 10,000 RPM Hard Drive and a separate 250GB 7,00 RPM drive seems better than QUAD Core 2.66 Ghz on one 7,200 RPM Drive. What about the video cards?

System 1:
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Dell XPS 690
DUAL core Intel Xeon Processor 5160 3.00GHz, 4MB L2,1333
4 GB Ram
Primary HD: 80 GB SATA Hard Drive DataBurst 10,000 RPM Sata Western Digital Raptor
Second HD: 250 GB Sata II 7,200 RPM
nVidia GeForce 8800 GTS video card
Price : $2,000

System 2:
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Dell XPS 690
QUAD core Intel Xeon X5350 2.66GHz 8MB CACHE 1066MHz FSB
4GB Ram
250 GB EIDE SATA II Hard Drive 7,200 RPM
Nvidia GeForce 8400GS PCI EXPRESS VIDEO CARD
Price: $1,600