Before you spend a single dollar i would try to rethink what you really wanna do with it. As you already discovered - for DOSBox it's just fine, can really run everything with it and not have problems.

Sure you could add a geforce 9XXX and have a wide variation of games from the early 2000s. But are these really what you are after?

Yeah you could hunt down a geforce and some RAM and maybe even a bigger HDD and whatever. Of course you could also install Windows 7 - but how much fun is that actually on a singlecore? AT least after you installed a virus scanner you will probably not have too much fun with it. A used dualcore system is like 50-100 bucks on ebay so maybe before you start spending a small fortune in parts I would think about selling the system and rather buying a new one. For a "gaming machine" as in "halfway recent gaming" it sure is a bit aged. Imho you'd have more fun with a beaten-up dual or quadcore and just throwing a cheap geforce 430 GT (like 50 bucks) into it.

Nah, this is going to stay just a dedicated dosbox machine for now.

I've pulled the mx4000 and the SB card and am running it now just on the onboard stuff which is more than enough for dosbox and playing pandora in the background, which is really all I ever do with it.

The parts went back into the P3 machine and I'm going to try and get that built up. No idea what I'll do with that though. It has an agp slot, 2x only though. I do need a 9x machine and this would be perfect for it, but I need to figure out why it's so flakey. Just tried booting it all up and everything comes on, but I'm getting no image on the monitor or post beeps, so I need to play around with it more.

There could be something wrong with the PSU, but it's also possible that something internal is not plugged in properly.