on behalf of all posters here I have to thank you for posting links.
Looks like an awesome system, with the exception of your 9200, which will work just fine in 8x mode - weather or not it will utilitize full potential can be easily argued.
It should be your first upgrade consideration, may I suggest:
EVGA's 6600gt <$200 @ zzf link>
Asus' V9999GT/TD GeForce 6800 GT AGP 8X 128MB <$315 @ zzf>
- an interesting mid-range hybrid
the BFG GEFORCE 6800 GT OC 256MB <$400 @ buyxg>
a hands-down great performer (I have one)
Also, as a personal preference I would probably choose Nforce 3 over K8T, but from what I have read about the K8T Pro they had fixed a lot of the original K8T's flaws so perhaps is not such a bad choice.