What do you intend to do with this machine and what is your budget?
FYI, the amount of memory on the GPU tells you little about it's performance.
You can locate AGP cards with Native HDMI
from $50 or pick up any card with a DVI Port
and a $7 DVI => HDMI Adaptor
for a few bucks less.
If you think your system is still halfway decent and want to keep it semi up to date for gaming, look into this 4670 AGP
card for $100.