Is my computer up to the job?

Since upgrading to a widescreen monitor (22") and moving on to the FS9 ifly 737 NG, I have noticed significant drop on FPS. On the ground especially at addon airports, I'm getting around 6-10FPs.  In the air and using default wx I can get up to 25FPS.  I would like to be able to run Active Sky and FS2 Crew and to add a second monitor to run FS commander 9.  I have a dual core CPU E2200 @ 2.20ghz with 2.75gb of Ram the video card is a NVIDIA Geforce 7100/Nvidia NForce 630i.   I'm perfectly happy with FS9 especially with the advent of such addons as the 737NG.  Would replacing the video card with something like a GTX 460 help matters or would I be better off upgrading the entire computer.  Grateful for any advice you experts out there might have to offer.