Well, the answer is it kinda depends...
As far as heat, how hot are you running now? if you're in the low 40's at 1.1 GHz. then you've got some headroom with that HSF combination. If you're already pushing up into the 50's, get a new cooling solution before you push it.
As for how far that chip will go, that depends on the stepping. You can read about them here -
http://www.athlonoc.com/stepmadness.php
Finally, is your chip unlocked? If not, you'd have a much better chance of making higher numbers if you unlock the L1 bridges allowing you to change the multiplier.
The A7V133 can go as high as you like. 12.5x is the max multiplier but you can combine that with the FSB speed to get some large overclocks. Stay away from the current BIOS offered on the Asus web site however... Using the 1003a BIOS I easily push my 1.4 GHz. chip to 1.55 GHz. on standard voltage. Upgrade to the 1007 BIOS and half the time it won't run at 1.4 GHz!
Scout