As the above posters have pointed out, there are no amps/receivers that include the necessary codecs for HD-DVD/Blu-Ray.
Afaik there are no forthcoming units that will feature them either. However, these codecs have been announced (click
here for info on Dolby’s TrueHD) and therefore I would expect manufacturers to start including them in the next iteration of their receivers i.e. Denon 3807 etc.
However, when released, some HD-DVD/Blu-Ray players should come with the necessary codecs on board. Therefore even if you bought a receiver now you could still benefit from HD sound, it will just be the player doing the processing instead of the amp. Hope that makes sense!