You answered your own question. You said '7300GS'. Therefore, it is NOT a 7800 series card. The 7300 series blows if you're wanting to run new games at good resolutions and framerates.
What you mistaked it for was the 7800 series, that is not a gaming card at all. Though, I do reconmend purchasing a 7800, or a 7800GT, maybe even a 7800GTX.
The 7300GS is overpriced too... My X700 got 2700 on 3dmark05 and is 96 on newegg last time I checked. It should be ballpark 80-85, but since it's new, they have to make a turn-around and sell some before everyone realizes that it shouldn't be part of the 7 series...