I am deciding between (so far) the yamaha 1400 and the denon 3805. i have 2 sets of speakers boston accoustics (main room) and Mirages. Which receiver would sound best with these brands? Also I have an old yamaha that i like but don't love. It is very reliable though. I like that the denon has 3 componant video ins. But the Yamaha is THX select. Does that matter? I listen to music and watch movies equally. Also is the automatic set-up on either system considerably superior (i can never get the delays and levels right in my weird shaped room) HELP PLEASE!!!
I would add the Marantz SR7400/7500 and the Harman Kardon AVR630/635 to your list.
IMO THX is overated as a useful gauge of sound presentation. Since you are 50/50 as far as music and movies go, I would stay away from the Denon or Yamaha. They are not as musical as the Marantz, HK or Pioneer Elites.
1. The Yamaha is a very poor match sonically with your speakers. You have not specified which Bostons you own, but if they are from the VR line (with the Lynnefield tweeter), they will tend to be rather bright and agressive. Now, as a company, Mirage makes speakers that are somewhat bright and aggressive as well. That means a receiver such as the Yamaha, which has a certain brightness to it will make the speakers sound harsh and edgy. This is not a good thing.
2. The Denon has a rather dry, cold sound that is also poorly suited for your speakers--not recommended.
3. I whoeheartedly agree with Bleustar here that a much better match is the Marantz 7400/7500. The Marantz is much warmer sounding, and this will smooth out the agressiveness from your speakers. This is not a criticism of your speakers, but a recognition of their sonic charecter, which you need to understand so that you can match the best electronics.
4. I also like Bleustar's suggestion of the Harman/Kardon 630/635 even better. The H/K is even warmer sounding than the marantz and I think it is the best combo for your speakers. H/K is also one of the best built receivers on the market, with overbuilt power supplies and outputs, which makes for a better sound as your amp is never straining (a more common problem than you might think). But you need to audition both to see which sounds best to your ears. Also, take a pair of your speakers in when the dealer isn't real busy. A good dealer will have no problem with you bringing in your own speakers to see how they sound with one of his receivers.