Since you're not gaming, the crappy x600 isn't a problem, and other than that, you've built a nice system.
I also have an x600; just not the AIW. I have overclocked it to 565/620 MHz core/memory from 450/580MHz core/memory on the stock GPU fan with no VRAM heatsinks, which is probably why I can't overclock the memory higher. The GPU also has a wussy little fan which I'm soon going to replace.
It's been nearly 5 months since I built this up, I run XP Pro:
AMD Athlon X2 3800+ 2.0 GHz (running 2.5GHz easily)
DFI nF4 SLI-DR mobo, cpu running 4.25v, 250 MHz x 10
2GB (2x1GB) OCZ Platinum DDR500 RAM (running 1:1, 250MHz, 3-3-2-7, 2.6v)
OCZ 520ADJ PSU & Aspire X-Cruiser Case, Red
ThermalTake Thunderblade 120mm rear fan 78 cfm 21 dBA
3 x 80mm Logisys CF80UVBL fans 35 cfm 24dBA
ATi All-in-Wonder X600 256MB video
Audigy Soundblaster Pro Gamer sound
3 x 250GB Western Digital SE16 Caviar SATA II HDs, 16MB buffer (non-raid)
NEC 3540A DVD DL writer & Mitsumi 7-in-1 floppy/card reader
Philips 190B6Cs/27 19'' LCD monitor
Logitech LX500 wireless key/mouse set
I am thrilled by the results. Any considering running dual processors, it is soooo worth it. Not only for now, but for Vista. I can edit photos in Photoshop and burn a cd in the background with no lag. Even while running disk defrag or something else too. Gaming while doing a full backup, you get the idea.
If I could do over, I might not get the Audigy card, the on-board Karajan Audio is pretty good, and I don't use my puter for hi-fi. I wouldn't change much else, maybe get Hitachi drives instead of WD, I had two warranty replacements with WD for bad drives, so QC doesn't give me any confidence with WD.
My total cost was about $2300 including monitor, operating system, and all components with tax/shipping. I can run 2.68GHz stable forever, just step it down to 2.5GHz to reduce wear, voltage, and heat. DFI mobo and BIOS are the best, and I love OCZ for the PSU and RAM sticks. I can't believe this DDR500 can run up to 2.7GHz (divider brings to about 275MHz) at 2.7v and like 3-3-3-8 settings or something.
Obviously my bottleneck is video card. But it has tv tuner and can TRANSFER my camcorder dv tape movies to DIGITAL without any additional adapters. And I don't use gaming much- photshop has NO lag at all. Far Cry can't go max settings, but UT2004 can go maxed out beautifully. Plus, my vid card was only about $120 after rebate.
If you are building a rig, drop me a line. Cheers.