I have a *RETAIL* Radeon 8500 that's running at 250/250. Would it be safe to flash it to 275/275? Tried powerstripping it (275/275)and noticed extremley minor artifacting, was wondering if the flash would bump the voltage and bring my Radeon 8500 back up to speed. Would I need another cooling fan at the bottom? And Most important! Will my warranty still cover me?