Before you buy a radeon, (esp. if you want text overlay), I would reiterate a prev. post: EW (Jeff Taylor) didn't like the radeon cards, didn't get clean (fast) frame rates on video transitions and the like. The list quoted above is a little old (in that in mentions MX440 cards). If you're buying a new card AND will be using EW, just buy a Nvidia.
Read this
post in their support board.
Ensure that it has a dual RAMDAC (basically dual processors) and that the 2nd port is accelerated/supports Direct X. I have a couple of the ti2400s, with dual displays and AGP cards. Nvidia seems to be the best IMHO (esp. wrt EW).
Since you're spec'ing a desktop, you can put anything you want in it!!