I just purchased an ATI HD tuner for my pc. Essentially, I need to know what is the best way for me to have digital audio. Currently the only sound I have is coming from an onboard sound card and factory speakers (yes, I need to upgrade). Here are some of the questions that I am asking:

Do I consider purchasing 5.1 speakers with built-in decoders and multiple inputs?
Do I buy an external decoder and some speakers?
Should I just purchase a high end sound card for my pc and let it do all the decoding (my only concern here would be the inputs ie. I have a couple of gaming consoles)?
What additional decoders do I have to buy for my PC, if any, to accomodate my digital audio choices?
Finally, what products do you all have to go with your suggestions for above?

PLEASE HELP!!!!