Looking for a new game.

I just got my new computer so I want some pretty good graphics. Graphics aren't everything though. I want a pretty good story and decent gameplay at minimum.

Right now I'm playing Mass Effect and so far I love it.

My specs if you need:
Amd Athlon II X2 Dual Core 2.8Ghz
GeForce GT 220 1GB
4GB DDR3 RAM
DX9 and Windows XP

I was looking at The Witcher or NWN2. Are these any good? I'm open to any suggestions.

both are good IMO
you should also try Dragon Age Origins

What detail level could I play DA:O on? I heard it has excellent story lines and great graphics so I don't wanna miss out.

Gotta get that full experience! :D