I got a DVI-D Single Link Cable to work with my Hit 57SWX20B & ATI Radeon 9000. Can't remember but there was some confusion as to which one (Single or Dual) but I read on here that another user had a problem getting the dual to work. I bought the single link and it worked for me so I'd recomend doing the same. Mine's made by Techcraft, and I got it from a buddy who owns a Mac store for about $40 CAD. It worked fine right from the start, albeit getting up to speed with Powerstrip and its settings was a different story.
Good luck. It took a while to get it set up correctly, but well worth it.
Scott
PS run my name "Scottwin" on this sites search page for my trials and tribulations ...