NOTE: The standard RCA ird that the previous person is referring to is model DRD-435RH, and while it does have an optical audio out, it only supports PCM digital audio, not true Dolby Digital. Any Tivo or HD will support Dolby 5.1 sound. Here are the makes and models of some standard D* receivers that support Dolby 5.1 sound:
RCA: DRD460RE, DRD480RE, DRD430RG/RG-A, DRD450RG/RG-A, DRD451RG, DRD455RH, DRD485RG, DRD486RG/RG-A, DRD486RH
PHILIPS: DSX5540
SONY: SAT-A50, SAT-A55
SAMSUNG: SIR-S75, SIR-S310W
Note that not all of these receivers are compatible with programming from the 72.5/95 satallite, though they are all compatible with 101/110/119 programming. Hope this helps.