The 8800GTS is a rather silent card, and as long as your caseflow is decent, the vga's fan will not speed up to a higher noise level.

The reason I recommended the 500-600 over the P965 is because I personally haven't been informed too much about the P965 northbridge. I have however read alot of reviews of the nvidia chipsets and from what I could see in the results and charts, they outperformed the Intel equivalent. However, it is solely up to you which one to choose. I can assure you that whichever one you go with (the intel P965 or the nvidia) it will be of great performance wise ;)