I used this one in a new (high-end PC) build a couple of months ago.
Gigabyte 2GB RAM ddr3 sdram Video Graphics Cards GV-N710D3-2GL REV2.0
Think was about $50 on Amazon.
You need minimal graphics processing for Hauptwerk, so a basic card will do. If you're doing gaming or other graphics-intensive work on the same machine, a much different need that someone else may be able to advise on.
Barry