Uriah, I am sure the new MC-501 is a great amps. I have not heard it, but the reviews are positive.
Before you spend some major $$ try actively biamping the 3.6R's with the CA400 on the bottom and 301 on top using a Byston 10B Sub crossover. Buy the crossover used. You can easily sell it off if you don't feel it's for you.
This kind of power will really open up the 3.6R's.
That's my 2 Cents
Uriah,I would highly recommend the new Pass Lab's 350.5,which I did a review on recently here on the GON. I won't restate the content of my review,but the the 350.5 is the best amp that has ever powered my MG-20Rs.It replaced a Edge NL-10 that is quite an amp itself but the 350.5 was much better in my system. I do bi-amp my maggies but the Pass should have no trouble powering your 3.6s. The new .5 series is not just an improvement over the original X series but a qualitive shift towards the reference of live music. I hope you at least include this amp in your audtioning process,I think you might be amazed. It retails for 9500.00 but you could get one for less with the right dealer.
I have heard the McIntosh 501 monoblocks driving the new B&W 802D and it was quite good. I took the 501's home to try on my Aerial 20t's. Great midrange, instruments had plenty of space and soundstage was excellent. Bass control on my aerials left a little bit to be desired. A very, very little bit. My current Levinson 33H/336 bi-amp combo is still in place......however I was very very impressed with the 501's overall. Very tough to go wrong with these if they work in your system.
Best advice I can give you is try before you buy. Dealers in my area are discounting the 501's to about $7200+/-
Take them home and try 'em.
Have a listen to Jeff Rowland's 501 mono blocks (500w/ch), they have the power and musicality to suit your B&W802s. Don't let their small footprint discourage you. These sexy looking amps sound wonderfully muscular and refined driving my father in laws B&W803 in a large living room. They also sounded great driving my B&W 804s, however I own the smaller version Jeff Rowland 201s (250w/ch)which sound similar.
McCormack DNA-2 Revision A, Gold, or Platinum. You may be able to find one at about half the $9000 price.
Ayve V-1xe should be on your short list as well.
That's where I ended up. The Pass will do a good job, but still despite the hassle of toobs, they are still best sounding. Not a lot of choices though. VTL, Manley, ARC.
ARC at 300 watts being the lower powered of the bunch. The Manleys do a splendid job on mine.
Trust me I know what a pain toobs can be.
I would look at Steve McCormack's DNA-500. Incredible power, detail,imaging and musicality for $7K list. I'm driving 4 ohm speakers effortlessly with the DNA's 900w into 4 ohms.
your 9k isn't going the dramatically improve your system. those classe's are nothin' but fine(i'm a mac person too). a change will sound different of course, and the macs are beautiful,but shoot the dough on something else.
My First Choice - Try to find a Used pair of Lamm M1.1's, M1.2's or M2.1's or M2.2's and you will never look back! endless current!
The Rowland 501's would also make a nice match and they don't generate any heat.
Lastly tireguy used Parasound JC-1 monoblocks to power his 3.6 and loved that combo. these run class A to 25watts.
I am driving a pair of B & W Nautilus 800s with a McIntosh MC 402. It sounds wonderful. It's hard to imagine there's anything out there that could make B & W speakers sound significantly better. According to the blue meters, I am operating at about 50% of the power when things are getting too loud. I haven't heard the 501s, but I hear their sound is outstanding, too. I would imagine they either equal, or more likely, surpass what the MC402s do. However, the MC402s are several kilobucks cheaper.
Check out the new Belles 350A reference monoblocks.http://www.powermodules.com/newdev.html
Also the Belles 150A reference monoblocks are excellent as well.SoundStage double reviewer's choice award http://www.soundstage.com/revequip/belles_150a_reference.htm
Some reading this may be interested in "great-but-cheap". Well the already mentioned Belles; but the older 150a hot rod at about 800,used, is killer. Cool running summer amp. I can only guess how the ref. amp sounds.
Try to audition a c-j Premier 350 ($8500).
I do not know about your Maggies, but I know of several dealers who frequently pair Rowland with the B&W Nautilus line.
Art SLA 1. New for $175 on Ebay. Can be used as an integrated. I owned it at the same time I owned Parasound JC1 monoblocks. The ART SLA 1 is 90% of the JC1's. I know many will think me nuts. Just need to put a good power cord on it and better speakers posts and RCA's.
H2O Signature monos - read the review at 6Moons.