My vote would go to Marantz and NAD. Denon and Yamaha are both thin sounding compared with the other two and do best with full sounding warm speakers like Paradigm and PSB. By neutral to my ears you are talking about Dynaudio, Monitor Audio and Klipsch because they tend to transmit exactly what the source material is without any alteration. If it's good it sounds good and if it's flawed you hear the flaws. This is not to say Paradigm and PSB are overly colored or colored at all. I like both very much. Proper matching is just so important as you seem to understand by your question. I would also add Elite to the list of what goes with a neutral speaker. My Elite/ MA system is a real joy to listen to, both for music and movies. I would also add that the new Yamaha 2400 is a much nicer sounding receiver than past models. Not bright anymore, just a bit thin.
Thanks for your answer. In fact, my speakers are Tannoys (I know they aren't broadly available in USA). I'm thinking to try the Monitor Audio Bronze but I don't know if I will have an improve in audio quality changing my Mercurys. So, if my best options in receivers are Marantz and NAD, which model I can take, considering I don't need too much power? Marantz 5400, NAD T752?
Both are very good receivers with good power supplies. The Marantz perhaps slighty warmer sounding than a more neutral NAD. I'd suggest looking at the specs for both and deciding on options. Naturally a true test for you is audtion them both if you can.
if marantz is warmer than NAD, then i'd recommend AGAINST marantz. i found NAD to be too rolled off in the treble using NHT superzeros which are fairly neutral and have treble extension beyond 20,000hz. compared to mission m71s, the NHTs are alot less fatiguing and natural sounding.
i'd use my NAD with my overly bright mission M71s maybe, but found that i greatly appreciate onkyo treble speed and extension over NAD. i wouldn't use my onkyo with those missions or B&Ws which are a litle bit on the lively side (extreme treble) as is.
i can't speak towards onkyo bass extension though as i've only used minimonitors.
part of what is considered "neutral" depends at least a little bit on listener preferences. i'm not at all a fan of excessive warmth or gut massaging bass, so maybe to my ears, what some consider as thin sounding is just right for me whereas what others like sounds painfully bloated to my ears.
to me, magnepans sound VERY flat except for the extreme bass and treble regions where they roll off a little. otherwise, they are extremely flat sounding through MOST of the frequency range. i consider my onkyo/super zero combo to be tonally neutral as it sounds similar to maggies with just a little more bass (subwoofer) and treble extension. tonally similar, but nowhere near as fast or detalied.
going back to NAD sound, my zeros sound muffled and closed in and can't portray an image as well. if marantz is even warmer, then it would be a terrible step in the wrong direction for me.
"warmth" might be more pleasing to most people, but it isn't neutral. listen to $10k B&Ws to hear true neutrality. they might sound "thin" to many listeners, but that is what true neutrality is... no emphasis in ANY frequency. those B&Ws don't bloat the bass or lower midrange at all.
IMO there isn't a truly "neutral" speakers in the mid - low price range, but I think that my Tannoys are more neutral than other brands like Paradigm, Infininy, Kef or Polk. Sure, the best test that I can make it's hear the Marantz and NAD side by side, but my problem is that it is difficult to find equipment NAD in my country, for that reason it is that I need people's advice that has already made this comparison.