Very nice, I've got very similar build for my pure XP rig.
Xeon x3320 2.50Ghz (pulled from a dead server)
Asus P5N-D (750i chipset)
ASUS GeForce GTX590 in SLI
4GB Crucial Ballistix Tracer DDR2 800MHz (with flashy lights!)
X-Fi Titanium Fatal1ty Champion
Unsexy HDD's and DVD pulled from work computers.
Corsair Obsidian 800D case with nice simple design like yours.
Yeh SLI isn't efficient but is is sexy, that's why I went for the 4 GPU setup not that XP can even support SLI. I do have a pair of EVGA GeForce 7950 GT2's the last dual GPU card that supports SLI in XP but got used to the performance of the 590 so swapped them back.
This is the most modern PC on my retro lan and also has a gotek floppy. It's definite my most used PC either as a support role for the older machines or playing games with detail turned up as much as possible and still getting great frame rates (GTA SA is probably the most demanding)
I do plan to upgrade to a dual LGA1155 system once prices come down though 😉