I too used to have a 170 WPC Denon 58** receiver and could never get it to sound the way I wanted, that being analog and warm even using it as a pre and using my Krell monos on the fronts. I started researching pre pros and bought a used B&K REF 50 on A'gon for $1300.00 I then purchased two Odyssey Stratos amps from Klauss
http://www.odysseyaudio.com/ a two chanel and a three chanel and have never looked back. Denon says their receiver was 170 WPC but I have gobs more power in my 150 WPC Odyssey amps??? Who's misleading who? Either the Osyssey amps are very very conservatively rated or Denon is blowing smoke! The total cost for both amps was around $2500.00 so for $3800.00 I have a very sweet sounding multi chanel system that I paid less for than I did for my Denon. The Denon is not even in the same county as the Odyssey/B&K combo let alone the same room. The difference is like a chevy malibu and a BMW 7 series it's that dramatic. The Odyssey / B&K combo forced me to sell my Krell two chanel amps and buy an Odyssey dual mono set up for my two chanel room. I my estimation no amp can touch the warmth, detail, soundstage & imaging I get from my Odyssey amps at even three times the price. Hell I sold my Krell's and bought the dual mono Odyssey's a new sub and a new tube pre for my two chanel room and still had money left over! I strongly recomend talking to Klauss before you consider buying any power amp. He will not build a five chanel amp because he says to build it right it would be over two feet tall! But you can get a two and a three chanel amp for less than most "under currented" big name amps.. If you are truly after sound quality amps are very important!!!! I would rather use a dedicated pre pro than a receiver as a pre pro due to the noise generated by the powersupply for amplification. My sound floor is now so low I actually turn off my flourecent indirect lighting when listening.....