How much did you pay for the 6800gt?
Ummm... let's just say a little over $300 for a BFG 6800GT OC. Believe it or not, it's getting hard to even find anyone still selling 6800GTs for the AGP format. I did quite a bit of searching, most of my regular stops for computer shopping (like NewEgg) don't even carry 6800GTs for AGP anymore.
I know the price to performance isn't all that hot, but I wanted as much horsepower as I could get for my AGP system because I really don't intend on upgrading this system for as long as possible. For most people a 6600GT is an excellent price to performance bargain. To be honest, I already had a 6600GT in my main system, but my wife needed her system upgraded and I wanted to bump-up my system as much as possible without going PCI-E (MB/CPU/Memory & GPU would all add up quite a bit). Believe it or not, I did notice a good jump in performance from the 6600GT to the 6800GT... more then I expected, and of course the 6600GT isn't wasted at all, as it went in my wife's system so we're both happy having GeForce 6's in our systems... the last upgrade for either of us for awhile (she has a 2.4GHz P4, and I have a 3.0GHz P4).
For the original poster, I would recomend (price to performance) a GeForce 6600GT, or hold-out for the GeForce 6800GS... it should be nearly $100 cheaper then my 6800GT and nearly as fast. Both should be good values... only shell-out for a 6800GT if you're crazy like me (and can even find one).