Help - How important is the center channel Amp?

I would say that untill you replace the rear channel speakers to voice match the fronts, I would go with a good 3 channel amp. Most of any shortcomings between the fronts and center you should be able to adjust them out with your pre/pro. You don't mention what amps you are using?

How many people for the theater? If it's one or two, I would recommend you do a phantom center and spend more money on the 2 channel amp. My personal reference system is using phantom center and I own the expensive well matched center and amplification, so it's not a cost issue. The quality of the sound is simply better in this scenario with the phantom center. This can only work though if your viewers/listeners are relatively centered between the main speakers. If they are off center too much it heavily degrades the localization of the dialog, and is not advised.

I plan on using the new Ayre monoblocks and either a Meridian 2 or 5 channel amp (I also plan on getting the Meridian G68 as the pre/pro).
Why is it important to voice match the rear channels? Not to be cute but there aren't many voices coming out of them. ie. isn't it mostly sound effects and background?
Also, importantly, the center amp issue seems to me to be an issue of quality not quantity (am I wrong here?) so I am not sure how the pre/pro can adjust for that?

I had given serious thought to not getting a center channel since most of the time there will be just one or two people. Now I am leaning towards getting one. Most music people seem to think its not necessary, but most HT people I have talked to say yes. And while not a primary concern, it does seem a little silly to have spent all this money but not enough if I want to show off my system, including a new TV, to a larger group of friends.

I have to agree with you on principle about the rear channels.

It is a good thing if you can use the same company’s products but you certainly don't have to use identical speakers for the rears.

The center channel is the single most important speaker in a home theater system. I am a Dali dealer and I would recommend you take a listen to them before you buy the Sonus. The Dali's are amazing for both music and theater and are a great deal as well, but back on to my point.

I installed a new cabinet in my video showroom, to house a 65inch 1080P DLP rear projector, and I had to modify the cabinet to house the massive Dali Euphonia center channel, but until I modified my cabinet, I had to use a much smaller and cheaper Ikon series unit. The difference in sound when I reinstalled the superior center channel was enormous! The superior center brought the experience to a whole new level of quality and involvement.

So hopefully this will illustrate the importance of the center channel, you want to buy the best center you can and one that will timbre match the left and right speakers you choose.

If you are going the way of doing any kind of real home theater do it right! A phantom center channel is not appropriate for anyone even contemplating purchasing the great equipment you are thinking about.

Also if you are really serious about music I would also go with a really good tube preamplifier to go with the Ayre or any other amplifier you choose. A tube preamplifier with a theater bypass will give you delightful music performance that should amaze you with the right ancillary equipment.

You would use the Meridian for surround sound with the front two channels going through the preamplifier. If you have a good dealer ask to try playing a piece of music through a good tube preamplifier and then to the amplifiers, and then listen to the same piece of music played directly by the Meridian through the same amplifiers, I am willing to bet you will find music played through a really good tube preamplifier to offer a wider soundstage and a delightful warmth and involving quality. If you haven’t listened to a good tube preamplifier you really should. You may want to listen to an Ayre preamp as well for the same test and see which way you like the sound.

As per the rest of the amplifier channels needing to be the same, they don't. I have over the years sold people tube amplifiers for the front channels with much cheaper solid state amplifiers to drive the center and rears, and both my customers and I couldn’t discern a real qualitative difference.

What you are building here is a music and theater system not a dedicated home theater, so unless you are a theater purist you have the flexibility to create some unique solutions.

Listen and let your ears be your guide.

When I auditioned amps for the L&R it was clear that the better ones made the speakers sound better. So if the center is the "single most important speaker in a home theater system", wouldn't it make sense then to buy the better amp for the center also?

I agree about about buying a better pre-amp for music. I wanted to leave something to look forward to.