High end (x1800+) ATI cards are notorious for running toasty. Cleeve wrote a review of the HR-03 on Tom's somewhere and I don't think it could handle the x1900xtx passively, but with a quiet 80mm fan attached I'm sure it would do fine.
Any reason you need absolute silence? There are many GPU coolers that are only audible over the most silent systems.
Arctic Cooling Accelero, Zalman VF series, HR-03, etc.