frankf,
having experimented with my system, and after several lengthy demos, adding a quality amp to a system will make a difference, and one that is worthwhile in my opinion. i have zero experience with yamaha receivers, other than a 20 min. listening session w/ the new 2600 this weekend. i have had 4 demo amps in & out of my system this year, as well as various other components, in a search for better sound. my system: denon 2805, klipsch RF-7 front & RF-5 rear, denon 2910 (for SACD & DVDA), cary audio DVD6 (for redbook cd & dvd). adding the cary DVD6 made a marked difference for redbook cd when using analog connections. it's not quite SACD, but for quality recordings its damn close, and while it's not a DVDA player, it also does a great job of playing those as well.
amps in order of preference: 1) cary audio cinema 5, 2) krell showcase 5, 3) B&K ref 125.2, and 4) rotel 1080. have also had a 2+ hour demo session w/ aragon pre/pro & i think a 3000 series amp with a set of RF-7. good, but not as good as the cary audio gear or the krell amp.
adding an amp can be an improvement, but the real improvement in sound quality was dropping the receiver and going to an amp & pre/pro, demo pre/pro i had was a cary cinema 6 and a rotel stereo pre-amp. after hearing the cary amp & pre/pro combo, using my denon receiver as a pre/pro w/ an amp simply does not produce the same sound quality as the cary combo. i really wish my receiver alone sounded that good, so i could quit spending money. but it doesn't, so i continue to search. however, i do like the receiver as a pre/pro using an amp better than the receiver alone, whether using a 2 channel amp to power the fronts & receiver powers the rears of using a multi-channel amp & using receiver as only a pre/pro. it's not a question of sheer volume, but of the quality of sound achieved using an amplifier. this is NOT to say that simply adding an amp will make your system sound better. the denon 2805/rotel 1080 combo did not sound better than the 2805 alone, but this may have been due to an amp that was not broke in. the 2805 paired w/ the B&K amp has a nice sound. best sound quality using receiver as pre/pro was w/ the krell amp, it did sound better than the cary amp w/ the receiver. however, it was not as good as the cary combo of amp & pre/pro.
from experience, find a dealer who is willing to allow you to demo whatever your considering purchasing. take it home & listen, from there your wallet will tell you what to do. if you don't like what you hear, you won't buy it. for real fun, get demos from several dealers at the same time & compare & contrast. this allowed me to quickly eliminate the rotel as an option, as i had the cary equipment at the same time. having 3 demo systems in your home at one time may start to cause the wife or significant other to look at you very funny, but when they could "care less" about your equipment (other than what your spending), and then out of the blue look at you and ask for you to go back to the other system because it sounded better, then your getting somewhere. i have also found that friends who could care less about stereo/home theater to be quite useful when they look at you and say "why does this not sound as good as what was on a couple of minutes ago." almost all of time i agreed with their opinions. different audio components can sound different from one another, even at the same power ratings, or whatever other specifications you want to look at. unless your much wealthier than i am, your not going to buy a component that doesn't enhance the sound quality of your system. if you can't hear a difference, or if it actually sounds worse, then don't buy it.
