I think the 450 will be great for what you have. I have a GTX 280 myself, which is slightly faster than that, and I am still able to max out all my games@1080p(except Crysis, of course).
I would actually consider a GTX 460 1GB or HD 6850 instead just so that you would have a decent card for games down the road. The price for performance scales really well for the extra performance that both the higher cards give.
Thanks for the advice. So the card isn't overkill for my CPU? I'm not that concerned about games down the road because I recently upgraded from a dinosaur (1st gen HP slimline) If it comes to the point where I can't play them at all, I'll upgrade the card.