Help! Recommend a card w/ digital out

I would appreciate your advice for what I want to do:

Must Haves:

I want to connect my PC to my Marantz SR7300 receiver using a digital
S/PDIF cable (preferably optical) in order to play wav files I have
stored on my hard-drive.

I would also like to play MP3s. Is it possible to send that through
the digital out? I am pretty sure my receiver won't know how to
decode MP3 so there needs to be a conversion from MP3 to PCM done
somewhere in the PC, be it hardware(firmware) or software. Can a
sound card do that? Or can something like Winamp do that? If that's
not at all possible, I guess I could live with stereo RCA connections.

Good to Haves:

I would like in the future to be able to play DVDs on my PC. I know I
need a video connection like s-video. From reading some of the
threads here, I believe some soundcards are capable of passing through
AC-3. What about dts? My receiver has both DD and DTS decoders.

Could you please recommend some sound cards that are suitable for what
I'm trying to do? Any that are both cheap and good? :-)

The reason I want to use the digital connection is that I would like
to limit the budget on the soundcard by not having high expectations
of the DAC on the card, as I am happy with the DAC in my receiver.
The only sound quality issue I can think of is that the card be able
to send the digital signal without too much jitter. Are there any
other specs that I need to consider?