I've OC'd that proc quite heavily,how far you are able to get depends on the chip,almost but not quite luck of the draw....
Nice work on your GT,sounds about right.....
I suggest some serious research before OCing the proc to much,if your PC doesnt post and you dont know what resetting the CMOS is,then you might be stuck for a while...As Angellus said you can simply raise the HTT or CPU freq but that will get you only so far,Once you raise it above 220 or so you will start having problems because the HT freq will be too high,or it might be on Auto which can cause instability etc etc etc,also depending on wqhat your Vcore is at default,aswell as having to disable thermal throttling and CnQ and depending on your ram you may have to run a divider etc....aswell as the limits for the stock AMD Heatsinks and general temps,mbo etc.
May the force be with you.