I don't know about that brand exactly... however, it seems pretty common at stock volts to get up to 850 or 875 core and a little over 1200 memory. My absolute max stable memory is 1210 but I've seen people running 1250 or even 1300 (tho, I don't know that I trust those numbers unless they volt modded their mem).
With a little extra core voltage, at 1.15V I'm running 960/1210 and I had it as high as 985/1200 with 1.225V. I was never able to get stable at 1000 core but then, in a furmark comparison with another forum goer here, mine beat his at 1000/1250 so... whatever that means.
Anyway, for beginning overclocking you should start by raising the memory speed and running furmark tests at 4xAA and ideally max resolution. With GDDR5, supposedly it doesn't error as easily but it does slow down if the mem is too high as it tries to resend the data till it works. If really too high it'll cause total lock ups or blank screen or sometimes BSOD. Just restart the PC and it should be back to normal settings (so long as you weren't silly enough to save the trial OCs and have them enable at start up). Once you get what you think is a stable mem speed, start raising the core. For core speed you'll know it's too high when artifacts appear. Once you think you're stable in FurMark, play some games for at least 30 mins and see how it's running. I've had FurMark stable and then freeze in STALKER: CoP... lowered the RAM from 1220 to 1210 and it's working fine.