Ok...I'm probably going to look quite n00bish here...but here goes:

My goal is that I want to be able to listen lossless multi-channel music, preferable from downloaded content from the internet. So my question is, based on what I already have gear-wise, what do I need to buy to achieve my goal?

Here is what I already have:
Sony STR-DN1010 (I read that the 3rd HDMI input on this is best for audio?)
Sony BDP-S570 (I know this will play SACD)
Computer with HD5450 that can bitstream
Also have a computer with a blu-ray burner if that helps

So, based on what I have, can I download for example multi-channel content like .flac or .dsf and play it via any method (like buringing a blu-ray or streaming from my computer) without buying physical SACDs or Blur-rays with content already on them?

Sorry if I'm leaving anything out or if this question annoys you due to the level of n00bishness.

Thanks for any help.