Tweak it the same way as everyone else. The only exceptional things you can do with that card are turn all of the video-related setting up to the highest setting without seeing much or any lag in the vanilla game. However, many cards can handle vanilla Oblivion at ultra high settings with all of the water settings set to high these days. :L
Basically, what I'm saying is, don't go crazy tweaking unnecessary thing in the Oblivion.ini just because of your system upgrade.
Oblivion.ini Tweaks - http://tescosi.com/wiki/Oblivion:Oblivion.ini#Tweaks
--Tomlong75210