My card was factory OC'd, so it came with the clocks at 590/800. You should be able to push up to about 640-650 on the core without a v-mod. You should also get 860-870 out of the memory as well without the v-mod.
At stock speeds of 590/800 I scored around 3000 on 3mark06. So you ain't too far off of that.
Keep on OC'ing... there's alot left in that card