My friend has damn near the same computer, slightly different mobo and he's SLI-ing. Oh, it's the dual core of that cpu though. Either way, you're in for a good experience, I didn't see if you were x2 the gfx card, but if you do, you'll be set for years to come. Cheers on that PC,
Nik is telling you some great stuff here man. I'd recommend ubuntu server, but only because I've actually used it
Once you boot your new PC, you can reformat your dell and install a linux server. I did it in under 20 minutes on a dinosaur and was in complete control of it from this desktop. Now, when I say dinosaur, I mean... prior not only to your dell, but prior TO dell lol
Your PC would be a pretty cool little data server, backup storage, place for you and anyone else plugged into your home network to share files (irregardless of internet connectivity, this would be quite literally more of an intranet, closed web group), you can even host a little page and open it to the world, or your own SAMP/CSS/MTA servers. That *might* be a little far for that dell, but I have Zero experience in hosting game servers and I ONLY have HEARD about "how powerful a server needs to be to do dynamics" etc. I'm sure it's not as bad as I imagine.