The Emo amp is very good for the money. Or you might investigate the new Sherbourn 8100 receiver, on-sale right now. Both Emotiva and Sherbourn are owned by parent company Jade Designs...
I tried responding to this 3 times at work..must not like that computer...
I don't know your speakers, but the 'brightness' tendency you read about is real. Yamaha is that way. I had a Yamaha AVR running a Yamaha outboard amp, powering Infinity Speakers with a ribbon-style tweeter. The highs got harsh and almost uncomfortable at higher volumes. Replacing the amp with an Odyssey Stratos, even though it was rated at the same 150wpc as the Yamaha, took away the harshness, and brought out a whole new sound quality in the Infinitys. I now don't have any need of my subwoofer when listening to 2 channel, and the highs are now smoother and far less fatiguing.
Emo amps are known for bang for buck, but I also read they can be 'bright', so depending on your speakers, and personal preference, that may be something to be cautious of. Someone who knows your Monitor's would have to weigh inm I can't help there. The other factors are room size and the environment - hard surfaces, little furniture? Soft carpet, over-stuffed couches? Those factors will effect your sound as well.
I would use a Onkyo. Why? very simple, because Onkyo and Monitor Audio can give a deep stage. This makes your stage bigger. Yamaha and marantz are both 2-dimensional brands. This means there is almost no depth or maximum of 1 metre. Onkyo has a more sharp focus compared to the brands which are mentioned.
Congrats on your MA's - you have three very nice speakers for your front soundstage.
If I read your post correctly, you are looking for recommendations on an AVR to be used as a pre/pro and a 3 channel amp. If this is correct, why are you worried if one brand is more "bright" than another? You are not using the internal amps of the AVR. If there is such a thing as an amp being too bright with a pair of speakers, it lies in its power amp section and its ability to deliver proper current to all frequencies under the varying loads the speaker is constantly imposing.
Since you plan on using a 3 channel power amp, the only thing you need to worry about it in the AVR is a full set of pre-outs and room correction. Do you prefer the Audyssey system that Marantz and Onkyo uses? How about YPAO that is proprietary to Yamaha? Finally, might as well throw in Pioneers advanced MCACC as many prefer it over Audyssey.
Finally regarding 3 channel power amps. This should be easy - there are not that many 3 channel power amps to choose from. Here are a few that come to mind from least expensive on up:
Odyssey Stratos HT-3
If anyone knows of anymore, please let me know as I am interested.
I have a pair of RX6's; currently using a Bel Canto c5i; I had a pair of Silver 5i's and used a CJ MF2250 and Cary CAD 200. At the time, I also had a Parasound Halo Pre; my brother has a pair of Silver 5i's and is using a Cary tube pre (CAD 308) and some kinda Class D amp he bought from Amazon (don't ask me why, that's just how he does things).
All combos have been excellent. The Cary had the least "slam."
Important to note: I *do* use an MA subwoofer. I have it rolled way, way back, but it does make a positive difference. By way of comparison, I recently heard Focal Aria and Nola Contender-both had way more bass, but were less transparent. If I flip my sub on, the Monitor combo smokes both those speakers for less than half the price.
You've made an excellent choice in speakers. Have fun with the source components. I have a feeling Jolia would pair nicely with MA, but that's speculative.