Shamu,
At the very least, you are going to need a nVidia GeForce 6600GT or I believe a Radeon X1350 or X1650. Some of these, I believe, can be had for under $75 at Newegg.
I'm in a similar situation, I have a X800XT PE that I bought two years ago that is considerably faster than the minimum requirements for MoH:A. The problem is that the card does not support Shader Model 3.0 (neither does yours) and is therefore useless.
If I want to get a card that supports SM 3.0 and keep my current performance levels where they are (which I want to do given I use a 22" widescreen LCD @ 1680x1050), I would need to spend $180 for a 7900 series GeForce. I'm still running AGP and have little interest in upgrading the entire system for this game, especially if I don't have to.
Therefore, I am holding off on doing anything. If the game is good, and people start playing (especially the [420thSS], who have taken a keen interest), I'll do what I need to do to get up and running.
I have some CPU headroom and may pop in a different processor if I can find one cheap enough. The disadvantage is that the processors I need (Socket 754) are hard to find cheap.