The rig is fairly balanced as is, but likely best at 2 year old games....
I'd be hesitant to dump more money into just a new video card (GTX460-1GB) where you might still end up CPU bound (but might be happy with higher res performance with decent settings), but, that would likely be your best bang for your buck, barring just saving/waiting for a new DDR3/i7-2500K based rig....
The system is well balanced. Just use it as long as you can stand it and replace with a completely new computer. More RAM won't make it faster. An ssd will decrease load times, but with the connections such an old motherboard has, it may not perform as best it can.
Ok.. so I may just make a second computer... Looking around on the forum.. I wanted to spend about 500. so I found....
The System Builder model made in late December. Is this still a good model to follow:
AMD Athlon II X3 445
Mushkin Enhanced Essentials 4 GB (2 x 2 GB) DDR3-1333 (PC3 10600) Model 996586
Sparkle SXX460768D5UNM GeForce GTX 460 768 MB
Samsung Spinpoint F4 HD322GJ/U 320GB SATA 3Gb/s
Antec NSK 4482B Black
Antec EarthWatts Green 380 W included w/ case
Lite-On 24X DVD Burner SATA iHAS 124-04