What is the best premp for Atma-Sphere MA-1 3.3 amp?

@chungjh  Yes I tried the Sanders Magtech amps then tried the Bricasti M25 amps. Bricasti brought out more 'soul" to the music so used 2 x M25's to drive the 10e speakers. (My opinion is using 2 of the same amps on the speakers is the smart thing to do....Roger Sanders may/will disagree). Yes the magtech has more power but the Bricasti never had a problem with my listening levels at 85-92 dB and peaks in the high 90's.    
(Dealer disclaimer)

@OP
I just did a quick google on the m545's ( I don't know which level you are using- Audiophile/Majestic/Ultimate, not that it seems to make a difference in power requirements). All seem to be 50-500 wpc.
So, the MA-1 should have plenty of power- unless you want rock concert levels.
The Sanders and Bricasti seem to be SS amps. Are you interested in SS?
Bob

I don't listen at rock concert levels. Some people have recommended Pass X350.5 for SL because of its "tubey" sound despite being SS. But as Ralph at A-S stated, at bass frequency, impedance is 30 ohms and X350.5 is only putting out about 90 W. SS is fine with me, but it seems to me MA-1 will give more even SQ across the frequency range. Of course, X350.5 is giving out 350W at 8 ohms in the frequency range where most music lives and is therefore much more powerful than MA-1. Then the question is whether I need 350W in the flat portion of the impedance/frequency curve if I don't listen at rock concert levels and my room is medium size 400 sq ft. What do you all think?

@OP,
In my limited understanding of such things, amplifier power ratings are for ballpark estimations of a speakers demands/capabilities.
The real issue is how well an amp can handle transient power demands. Which is why I lean toward having an amp leaning toward the higher power ratings.
Your speakers are rated for 50-500 wpc. Both the Pass and Atma amps fall nicely in the middle. And, given how Mr. Pass tends to underrate his amps, I bet they can put out a bit more power without issue of clipping or distortion.
Now, the reality check:
Unless you are really cranking up the volume, I doubt you will be using more than a few watts with normal listening.

So, why get an amp with 140 or 350 wpc?
Like I said, it is the ability to handle the transients within the music, and not taxing the amplifier to the point where it introduces distortion.
Like I said, I am no expert, so there will probably be some disagreement.
Perhaps Almarg can provide a better description. He knows and can write a very clear explanation, if anyone can.
Bob

thanks gdnrbob

May be people with experiences in both tubes (especially Atma Sphere) and Pass Labs can chime in. In <40 HZ, A-S MA-1 is more powerful than Pass X350.5 (for Soundlab), but X350.5 is more powerful than MA-1 everywhere else. Did I get this calculation right?

Obviously MA-2 would be a great solution (220W), but it is mucho $$$$ especially if I don't listen at rock concert levels.