would upgrade GPU have any positive effect on gameplay and performence

I recently upgraded from 4 to 8GB of RAM and it made all the difference in the world to game play. Even playing 1v1 on single planet systems w/ 4GB, most of the time I wouldn't load the UI until 30-45 seconds after forced landing of my commander. Now, I beat most opponents into the game. I run at minimal graphics settings, 100% rendering @ 1920x1080, don't pay attention to actual fps, but framerate stays playable in all but the longest of games.

My system, for reference:
AMD Phenom II Hexcore (1055T@2.8)
AMD HD6770 1GDDR5
8GB GSkill DDR3 1200