Video Card Recommendations

[MNMax21]

Okay, I might've made a slight mistake in planning.  I built my cabinet and have a 4 player control panel.  I love it, but I recently got involved with downloading pinball games from VP.  I have got them all working now.  However, I think my on board video is really holding back the experience.  I end up having the pinball disappear at certain points of every table and the graphics almost look like they're ghosting slightly.  It has almost a pixelated look to some parts of the table. 


I have a HP Compaq CQ5826.  It has a AMD Athlon II X2 3.20 Ghz processor  (It's a A3 socket) and an onboard ATI Radeon HD 3000.  I bought this on the cheap and will end up needing to buy a new motherboard (lack of slots) in order to upgrade my video.  I would like to keep the processor if possible and just switch out the motherboard and upgrade the graphics card.  I am wondering if anyone can give me a good recommendation on a middle of the road video card??  I really only use this machine for Gameex, MAME and VP/FP Pinball. 

I use a 32" LCD TV