When you say digital out from your PC, are you talking just a S/PDIF in coaxial or optical on the back of your sound card?
If so, you don't have to worry about MP3 decoding in your receiver. Any sound card outputting digitally through this standard type of interface will be using standard PCM, which to your receiver is no different than the optical output from anything else. Some sound cards even will pass a DD/DTS six channel signal through their digital output. Mine claims to, but I haven't tried it yet.
So, when you want to play MP3's, you start up Windows Media Player or Musicmatch or whatever MP3 software you happen to use, get your tracks playing, and the digital output coming out your sound card will be converted by your receiver.
All that said, I have seen receivers advertising MP3 decoding, and some even with a USB input that says you can stream MP3 files through that connection and let the receiver decode them. Frankly, I don't understand this. For one, I don't know how you get non-decoded MP3 data to stream out of any port on my computer. And secondly, why should we assume your receiver can do a better job decoding MP3's than your computer?
With sound cards having digital output going for under $30 these days, spending any amount extra on a receiver which will decode MP3s doesn't make sense to me. One could even argue that the sound quality of MP3's is poor enough that you might as well just use an analog connection anyhow...
Hope that didn't add too much confusion.
Aaron Gilbert
