The 9800GT is a little weak. You can get a GeForce 460 for under $200 now and it smokes the 9800GT. It will handle any game easily at lower resolutions (1680x1050 and below).
A game like crysis would crush that system on medium settings. Why not invest in a single ati radeon 6950? That would be a solid investment and allow you to enjoy the higher graphics capabilities that pc games have to offer. Here is where you can get one for a decent price. I have two of these in crossfire mode and it shrugs off all games ive played at 1920x1080 with tessellation and physx enabled. Im talking 50+ FPS averages at the very least. Newegg.com - XFX HD-695A-CNFC Radeon HD 6950 2GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card with Eyefinity