If you are unable to find a good HTPC card from someone here, my HTPC is running this Gigabyte HD4550 which is plenty powerful for an HTPC and is really inexpensive @ $39.99, just to let you know, ive been running my HTPC with it for streaming 1080p, and it doesnt require another power source.
Btw, the top part of the card IS removable, so it can also be a small form factor card.