so you're getting a VF900?
well, I'd about guarantee you'll be able to clock higher with it. the stock cooler is pretty weak (it's the same cooler that's on the reference 7900 GT's)
also, from my experience, coolbits is unstable compared to ATI Tool.
what drivers are you using? I'd try an 8X.XX driver (I'm using a tweaked 84.66 driver on my 7900)
I'm not certain, but ATI tool might work with a lower driver version (plus, I don't like the 9X.XX drivers anyway)