I can sure as heck tell you it isn't a bottleneck. Although your card isn't the most powerful card in the world, it should be doing a LOT better then it is. Fix the issue before attempting to throw money at it.
Despite your up-to-date drivers, I would bet this is a driver issue. Download and run driver sweeper to clean out all your video card drivers and reinstall the newest version.
Have you ever had high framerates in said games, or has your computer always been slow by the way?