Flashing your 6800 wouldn't be a good ideal. Why possibly ruin a $300 card? Theres no point in that.
Anyways, to unlock the last 4 pipelines, if possible, you can use RivaTuner. Most cards won't be able unlock the last 4 pipes, my eVGA 6800 can't. Some MSI's can, not sure about LeadTek.
Also you can overclock with RivaTuner, and if all goes well, you can set it to make these changes on boot-up.
This meaning you can expierment with all this stuff, with virtually no risk on destroying you brand new card.
My Desktop: <A HREF="http://Mr5oh.tripod.com/pc.html" target="_new">http://Mr5oh.tripod.com/pc.html</A>