Which power amp Bryston 3Bst, 4Bst or Musical Fidelity A3cr?

I have been upgrading my system lately. I use many sources CD, DAT, synthesizers and phono. They all have different levels. While I don't play very loudly some sources are too soft and need a significant boost. I am now using a Musical Fidelity A3cr preamp (which I love), TMC Yellow interconnects to the amp (a B&K Reference 4420 - 225WPC). My main CD source for now is an ARCAM Alpha 7se connected with TMC whites to the preamp. My speakers are Magnepan 1.5QRs. I think at this point the weak link is my B&K (a good amp, but now a little outclassed) and would like to upgrade. Tubes are not an option since I leave my system on all day and I don't want the hassle. I'm torn between the Musical Fidelity A3cr power amp - my only real reservation is whether this will have sufficient power. It is rated at 120WPC to 8 ohms (nominally only half my B&K which does not feel overpowered - but I know rating can be deceiving) The other option that seems attractive is a used Bryston - probably a 4B-ST (although a 3b-ST might be sufficient). Does anyone have any thoughts on how these compare or on the power issue with the Musical Fidelity ? Any other ideas welcome.

It's my opinion that Maggies do love current so the more power you can throw at them the better. My 4B-ST does a very nice job with my 1.5's - much better job than my 10 year old 3B did. While I have not heard the MF amp I would think that there would be some synergy using it with your MF preamp but I believe it could run out of steam against your current B&K amp (which I think is a really nice amp...) There are many good choices out there - Aragon, Classe, Marsh, Odyssey but in the end auditioning is the safest path to choose to ensure you get the synergy you are looking for...
I agree with Rgd. The Bryston 4B-ST is a very good match with Magnepan speakers. When Magnepan displayed their new 20.1 speakers at the Stereophile Home Entertainment Show they did so with Bryston equipment. They obviously think that Bryston is a good match with Magnepan.
That being said, I run a Classe CA-150 with my Magnepan 1.6 QR speakers. I found the Classe to sound a bit warmer than the Bryston. The low end was not as tight. I use a Sunfire Signature Sub so that is not an issue in my system. The other choices listed by Rgd may be as good if not better choices in your system. I have only heard wonderful things about the Odyssey Amplifiers and the price seems more than wonderful. I have heard many Aragon amplifiers and have always liked them.
I heard the Musical Fidelity Preamp at Audio Connection and thought that it was a very revealing preamp. You may do well by finding a high current solid state amplifier that falls on the warm side of life. Good luck in your search.
I own a Bryston 4B-ST and 5B-ST (which is the 3-channel version of the 3B-ST), and highly recommend the Bryston line of equipment. The 4B-ST has more than adequate power to drive your Maggies -- it is rated at 250 wpc, but typically produces 290-300 wpc. The Bryston 4B-ST is very clean, dynamic, and leans slightly toward the "cool" side of perfect neutrality -- no tube warmth here -- and it does a superb job with bass control. The 3B-ST is also an excellent amp, and many reviewers regard it as the best medium-powered amp that Bryston makes. The 3B-ST is rated at 120 wpc, but typically produces 150 wpc. Both amps are good enough to reveal any upstream weaknesses in your system. I have not had the chance to audition the Musical Fidelity amp, and thus cannot make a valid comparison.

If your budget will allow, I suggest buying the 4B-ST. It's a fine amp, and has an industry-leading, 20-year transferrable warranty backed by the finest customer service among high-end audio manufacturers. You can buy the 4B-ST for about $1600-1700 used, or you can buy it discounted from the dealer where I bought my 4B-ST. The dealer is "Bestofdeal", a clicks-and-mortar operation in Santa Clara, CA (look for his small ad in the back pages on Stereophile magazine). The owner is Danny Oovlin, and the easiest way to contact him initially is by E-mail at: bestofdeal@aol.com.