A couple of things come to mind.
1) Make sure you're at running 2.35 at post. The A7N8X Deluxe BIOS presets the CPU to run at a lower frequency. Or better yet tell us what you have it set at.
2) Run dual channel if your memory is capable of it. Set-up the Memory in BIOS correctly, or better yet tell us what you have it set at.
3) Laserth is right, with a killer setup and a mediocre video card you have a what's called a bottleneck.
4) What hard drive (s) are you running. That MOBO is capable of 166 hardrives and two SATA drives.
5) 1gig is better than 512
Run 3DMark2001SE benchmark and post the results. It's free to download, but 40megs big.