Sorry, all getting a bit 'religious' with this believer/non-believer language.
I 'stream' internet radio on occasion (via AirPlay from my iPhone and iPlayer). I also stream from my iMac (Apple Lossless via AirPlay) and it sounds absolutely fine. The iMac is in the adjoining room, so the - albeit minimal - noise from the iMac is not an issue anyway.
It sounds extremely good. Internet radio (from iPhone/TuneIn Radio Pro app) is even better quality than using the built-in internet radio feature on my Marantz (probably because TuneIn Radio Pro always finds the highest bite rate and uses AAC, where available, whereas whatever software the Marantz uses doesn't.)
I have the digital optical input (on the Marantz) connected to my TV for good quality stereo sound from TV, Blu-ray and Humax.
My criteria for streaming is convenience, lack of extra boxes, minimal cables and, yes, sound quality (but not to the point where I would invest in an extra DAC, seperate streamer, extra cables etc. just for the sake of what might be a tiny increment in quality.)
I have done with all that 'believing' and got a system that does exactly what I need with more than satisfactory results and a lot of enjoyment. We can even just pop in a CD if needed.
Four extra boxes, thirteen more cables and 17 months ago I worried about crap like this but frankly I don't give a toss.
I don't even recommend the Marantz M-CR603 anymore because it is inevitably followed up with "will it drive my 8 foot floorstanders and still be loud at the end of my 65 feet long garden?" type questions, or people insisting on wanting to use it without ethernet or with some flaky internet service that means you know they'll be on here next week blaming Marantz because they can't read the effing instructions and are never even going to get the initial firmware download completed let alone Spotify!
That feels better.