uummm......overclocking and flashing are 2 very different things, technically, in risk factor, as well as performance gains .....
Both can fubar your card if not done exactly correct, but o/c'ing is usually easier to tell if your about to do a goofy.....flashing OTOH is normally a "all or nothing" propostion.....it either works or it doesnt, and some times you can reverse it, most times you can NOT, & end up with a more worthless P.O.S. than you started out with
Having said that, BUYING a flashed card from someone that knows exactly what they're doing is probably a better idea. Using this method, I've been running a flashed 9800Pro in my QS for over a year now notta problemo, as well as using the linked app to eek a bit more oomphy out of it too