Sound quality on DishNetwork receivers

I have had my Dish 301 receiver for about 2 weeks & it sits alongside my 4DTV receiver. They are both plugged in to my surround/audio system & there is quite a large difference in the quality of the audio coming from both of these unit's analog outputs. The Dish 301 audio is not nearly as clean & full sounding as my 4DTV receiver. I have tested this with both systems on the same channels, plus it's just obvious from spending hours listening to movies & other broadcasts through the 301.

Is this a known problem with small dish receivers, or just a 301 "analog out" thing? Is compression an issue with the audio side of things?

I would be willing to spend the extra dough on the 501 or 6000 if the digital audio output makes for an obvious upgrade in sound quality of all broadcasts.
Anyone out there that has similar experience with the audio on this unit, or anyone who has owned both the 301 & 501 (or 6000) that can tell me if the sound quality is better with the digital output of those other receivers?

The DISH receivers have very bad DACs (TosLink on better receivers helps a lot), but it will never sound very good as it's 128 kbps MPEG-1, Audio Layer 2. Hopefully, Audio Layer 3 will eventually be added to a future version of the DVB standard and used (though it does require much more processing power)