Hello Rosty,
I am supprised that you are having that result from your 5803 to be perfectly honest. I was at CES in 2003 and Denon did a demo with the 5803 with no external power amps and they where using M&K speakers. They where using a DTS demo dvd and multi channel music to demo the flagship reciever. I never did at any time notice any distortion as they did push the reciever and after the demo it was cool to the touch. I am wondering if you got a bad unit? As far as power supplys go heck I have a Yamaha 995 reciever that I power altec voice of the theaters with dual 15" woofers, polk center with two pair of advent marbles for my rear channels and if the yamaha can handle that the Denon should handle what you have. Especially if it can handle the M&K's.
As far as the Klipsch speakers go I have set up a Yamaha reviever with Klipsch and imho it sounded great. But Adcom and Rotel should sound nice with the klipsch. If you want a serious multi channel amp that can run just about any thing and give you plent of headroom and clairity. I would highly recomend the Cinenova power amp that thing is a monster.
