I personally wouldn't go for a Dell at all. I've had some bad experiance with the Inspiron 8100 series (replaced motherboard a month after buying it, speaker problems, two burnt out batteries which cost me 250 euros to replace while still under warrenty, and over all shoddy build quality).
If you want to go with a PC in the end, the best way to go is to build one yourself. Get some good components and a decent tower. Some Panaflo fans to keep it quiet. You'll spend a bit more than the Dell, but you'll get a better computer in the end. Plus, since you have a copy of Windows XP Pro, it should be easy for you to get it running pretty fast without spending too much.
On a personal note, I sold my homebuilt Athlon 64 system to get a used PowerMac G4 "Quicksilver" to build up. Currently it's a 733MHz system, 1.5GB of ram, flashed Radeon 9800 XT 256MB card from a PC in it, 558GB of HD space (Raid set on a SATA PCI card, still have room for two more disks), Pioneer DVR-109 burner, USB 2.0 card and Miglia PCI TV card. The system runs like a dream, though i'm gonna try to finish up the upgrades with a dual 1.8GHz G4 processor card and a beefed up PSU (probably a 500 watt model for PCs). In a sense I've downgraded to a 4 year old computer, but i've got less headaches with it and with some upgrades and modifications i've managed to make a PowerMac that would possibly give a G5 a run for it's money.