Hi,
You may like to try vlc as a windows media player. I use it all the time across samba sharing as it is quick & clean.
As for sound out of the 350, how things are setup maybe your problem. You are making me assume things so therefore I can't give a direct answer.
If you have tv out enable (no computer monitor used) then the audio will come from the dongle cables. To have control over the audio levels from those connections, you would have to route into line in and then use the line out of your sound card to an amplifier.
If you are using a standard computer monitor then the audio should be on the line out of your sound card.
To besure the signals can get around properly, you should open an xterm window and then run alsamixer (alt x )at the $ alsamixer
The only thing you can't do with a single tuner card is watch "live" tv. Actually all tv viewing is a recording, so therefore you simply have to go into the media folder and watch what ever is listed as available
The hardware decoder I believe only works for the dongle connection to the tv. The computer display is only software decode. I could be wrong, surely won't be the first time.
Mike