My 2 cents...
A new video card would definitely improve your gaming and video editing. I guess it comes down to what is more important: gaming, video editing, or music recording.
I am using an xFx GeForce FX 5200, 128MB, AGP 8x. It was very reasonably priced ($60 4 months ago...might be cheaper now), and it does the trick. I don't game very much, but I do a lot of video editing and it works great for that.