Ken, I feel your pain...
I was at a friends house the other day, and my friends wife was like "I can't tell the difference between HDTV and regular TV on her husbands 61 inch Samsung RP_DLP. I was sitting right there.. the differencee was astounding. I don't think she knew how much hee paid for the tv...
anyway, I too like the denon sound. Yamaha's always sounded a little flat to my ears. I'm sure that with the right kind of speakers it really shines though. If I were you I would take advantage of tweeters trade in policy and buy one of them (the denon first

and audition it at home with the speakers you are going to use. If you don't like it, trade it in for the Yamaha.
But i'm with Ken. I have the 1803 and am really happy with it (well, it could have a little more power - especially now that it is driving 6 speakers - got my 6.1 setup going... yeah!). The 1803 was a big improvement over Kenwood.