The Shuttle has the ATI Radeon 9100 IGP (RS300) chipset which I believe only supports directX upto ver 8.1. It does not have an AGP slot hence you are stuck with onboard graphics. Read a couple of reviews which suggest this chipset can not run direct x 9. The benefit of this box however is it is very quiet with an extenal PSU. I am prepared to lose the AGP slot for a box that can sit under my TV without making a sound. I hope to have a TV shortly that supports PC VGA (XGA) so the TV out a AGP card would give may not be neccessary. I don't currently own this hardware so can't try direct x 9 for myself but the purpose of the box is to run GBPVR.
You can always install the latest DirectX software, although the graphics card may not be able to fully take advantage of the latest DirectX technology.