hdmi connection

IMHO and IME HDMI is not the best way to go. I have experimented with various outputs from my Denon Blu Ray player into my Denon AVR, and the analog outputs from the BDP sound much better than anything else. The quality of audio output from your computer depends upon a great number of variables, and if you have the option of other outputs, you should try them. I have used a PC rig as the head unit for my 2 channel system for over a year, and my current recommendation is to use USB output to the USB/SPDIF converter of your choice/budget, then go from that to your stereo. I think this will give you better sound quality than a dedicated audio card inside your computer. There are lots of options available at many different price points for a USB converter.

While I agree with most of what Realremo has said, let me add that MOG's 320kbps lossy stream may not benefit from an improved connections. Also, If your Marantz is a recent model, it may have a compatible USB input obviating the need for an external DAC.