First off, if you're going to fork out the dough for a 6800GT, you had better know what the hell AGP 3.0 means.
Second, PNY sucks as a graphics card distributer. They never put anything with their cards, and their service is just okay...not great. You buy retail from PNY and it's literally like you're getting OEM.
, keep in mind you're putting a market-leading graphics card into a machine with generic RAM, and a just-decent processor. Just keep that in mind.
Lastly, the old titanium (Ti) cards can't compare to the 6 generation cards. Unless someone's using a workstation Ti, I doubt they're getting better results (image wise) on their Ti over a 6800.
If you're a serious gamer, I would suggest updating your proc, mobo, and RAM, too. If you're not, I would suggest getting a graphics card from the level under the 6 series, which will be cheaper and do all you want.