While there is no doubt you can hear differences in different electronics, you also need the other features.
The DMC is useless as far as I am concerned for a processor receiver. I don't really care what it sounds like, it does not upconvert over HDMI (though they will give you an HDMI switch) and it's on board amps are not as powerful as an 805
I'm not trying to start a flame war here or anything, but the Onyko receivers are so far ahead of the DMR 1 it's laughable. If you don't have an HDTV yet, sure, go ahead and get one. But if you have HDTV and looking for a multiuse receiver - I'd go with the Onkyo, hands down. No contest.
Now, when the DMR-2 (or whatever it will be called) comes out - you'll have something to compare and debate about

. And as I mentioned already, if you don't need something to upconvert a video source, there's no need for the Onkyo, the DMR-1 will do just fine.