The last rear wheel drive Pontiac was sold in 1986. The Bonneville and Parisienne changed platforms after that year and no rear wheel drive Pontiac was sold for the next 20 years. Then along came the G8, a car designed to compete with the powerful luxury coupes and sedans from Europe.
So far, there are only trim levels on the G8: base and GT. The engine on the base is no slouch; it's a V6 DOHC making 261 horsepower, but the GT engine is a true monster; a V8 paired with a 6 speed automatic transmission that can propel this car from zero to 60 miles per hour in just a hair over 5 seconds. In addition, an even more powerful G8 is likely in the works. The G8 GXP is rumored to have the LS2 engine from the Corvette that makes over 400 horsepower.
The G8 is far too new to be making it to the used car market yet. Wait a few years and they will start showing up as the rich owners bring back their lease vehicles in favor of a new car. Keep on watching eBay for any new listings, and find parts for your current car in the meantime.