Re: would this be an ok upgrade?
^^ a bit overkill yes, but there will always be a bottleneck somewhere. But as a general rule, never get any of those pre-overclocked video cards. It's the exactly same card, only difference is that they have overclocked it. You can do the same yourself. No point in paying for them to do something that you can do in 10-15 minutes.
Anyway, your best options would be the 8800GT (256mb or 512mb) or the 9600GT. (just got this one myself a few days ago) Both are awesome for the price.