Dual AMD Opteron 248s Tyan K8W mobo

I'm looking to put together a new computer to replace my aging rig. I just now learned that my mobo only supports 28 bit LBA, and I have 2 drives greater than 137 GB. Accessing anything past 137GB corrupts all the data on the drive, causing me to lose a lot of stuff I download off of bit torrent. This is ****ing me off to no end. Old rig must die, and get stuck in my closet doing Folding.

This rig will also be the core of my multimedia center, with a projector attached, so I can play UT2004 on a screen 120 inches across. I want to be able to run 10-12 AI based scripts, and TIVO style recording on the second processor, and use the first one for HL2, Doom III, and UT2004, since it's directly attached to the PCI/AGP bus. Would some other processor/mobo combination be better suited to this?
My new rig will have the following, assuming I somehow get the 3k+ to buy it:
Dual AMD Opteron 250s <-- Is there any way to overclock these and not have to change the PCI/AGP bus frequency?
Tyan K8W motherboard -- Sexy PCI-64/133mhz
Expensive 1024 ECC Registered DDR400 memory modules
NetCell RAID Expander card via SATA w/ 5 WD250GB hard drives in RAID5 .9TB accessable space.
DVD9/BluRay burner (I'm not getting this anytime soon)
Water cooling for all active areas CPU/Bridges/GPU/MOSFETs/etc.
TV Tuner card with hardware MPEG2 encoding at 720x480
550W 24+8+6 power supply
Custom case, since there is absolutly no way I could fit all this stuff into one full tower.
ATI Radeon 9800 Pro
Creative Labs Audigy (pick one, I don't know yet)

My main questions are:
Can I overclock these processors in any way? If so, will I have to play with the AGP/PCI bus frequency?
Is there something that is cheaper, and does a better job?
Is this just plain overkill?
Do you suggest any changes to the hardware above? Why?

No, not on the K8W, there is no overclocking to be found.

I'd wait for IWill's new NF-based Opteron mobos to come out, which supposedly support OCing with a PCI/AGP lock. DK8N, AGP w/ 4x PCI-X and 1 PCI, should be soon, and the DK8E after that will have PCI Express 16x, 4x, 1 PCI, and 3 PCI-X I think. CPUs Id shoot for would be the 246 or maybe 248, the premium for the 250 isn't worth it, especially if you're OCing. Definitely go X800 over the 9800, thats an extremely significant boost. For RAM, Id go Corsair XMS registered, 4x 512 MB (you'd be hard-pressed to need to use more than that). For HDDs, if you're going to have this high-end a rig, do a RAID 0 or 10 of Raptors or Fujitsu/Maxtor 15k SCSI and then a secondary storage RAID 5 (you have the PCI-X, why not use it?).

Or-

Build two single rigs. One A64 w/ an X800 etc. for gaming, and then one whatever else you want for your secondary activities. Its cheaper and you'll have more tweaking room, especially w/ non-reg. RAM.