Mace - as another PA hunter you can rest assured that your .308 Gamemaster will take any whitetail cleanly and is also capable of killing an elk cleanly should you be lucky enough to get one of these cherished tags. Some other things you should consider is what else you plan on shooting with your new rifle. Are you going to use it for coyotes, groundhogs? If so, a .243 is good for these critters (a bit more than needed) but I guarantee you that with a 90 - 100 gr bullet, it will drop a deer about as quick as any other medium sized cartridge. That would be my choice if I were going to keep the Gamemaster. I would have to sit and count all the deer I shot with my old Savage .243 and 100 gr Hornady SPs pushed by 40.5 gr of IMR4350.
The most important thing though is if you really have the desire to get another rifle is to be sure it fits you. If you decide on selling the 760 for another rifle go with an '06 and let me know how much you want for the .308.