I'm now leaning towards an Atma-Sphere S-30 as perhaps my best choice. However, this choice may be problematic.
What finally sold me was a lot of additional research and uncovering something I had never known, and which is very unique. According to what I've read, all of the Atma-Sphere power amps have equivalent sound quality (assuming they are the current version, or upgraded to it) the difference is simply in power. Having heard some of their top amps, granted it was a few years back, that has me convinced this is the right way to go.
As for why the S-30 specifically? , Well, the M60's would drive my very small listening to temperatures that would make it impossible to use them almost half the year. Trust me, I had a friend who owned those in Chicago, and his room was larger than mine and still became very hot during extended listening sessions and were unusable in the summer.
And now to the problematic aspect of this. I don't know how many S-30's have been sold, but my guess is that it is not a terribly large number. I base that on the fact that they show up for sale so seldom here on Audiogon. Of course, their owners may be so happy that no one ever sells one? Honestly,though, I don't recall ever seeing more than one or two of these appearing for sale here in an average year. You see far more M60's and MA-1's, etc. And to complicate matters further, I would only want one of the older style Mk II's that are long, front to back, as opposed to the newer wide style models (I just really don't care for the appearance of the newer models). I would then send the unit off to Atma-Sphere to be upgraded to 3.1, all of which my budget can accomodate.
And to top it all off, last week, just moments before I was considering purchasing it and just risking that it would work well with my preamp (which Ralph has answered), someone closed a deal to buy one in mint condition for a very good price here on Audiogon.
So, in the end, please keep any recommendations or advice coming. While I can get by for say, a few months, I cannot honestly wait six months, or even a year for another S-30 MKII in great condition to pop up for sale, and may be forced to go in a different direction simply due to that reason. Things are never simple in the audio world.