Isn't the 6800NU a 'non-ultra' which would be a regular 6800? (was just a guess) Mind defining it for me?
And in my opinion, a 6800LE is better than a 6600GT 'if' you can find one that you can unlock to 16/6 (don't think its better stock though, same pipes and stuff) and maybe even oc it a little if you want.
Note: anyone reading this and doesn't know, ocing and unlocking stuff in your graphics card will void your warranty I've heard