Attempt to answer Q's
Anvil, sorry for the late reply, I don't really monitor this thread any longer since it has been overtaken by the Aleph-X thread and that there is no more activity here to speak of.
My way of thinking about the X- circuit and as I recall, that is the same way as the original patent describes it, is that that the circuit is a number of current sources. above and below the signal transistors. In a way you can say that the high gain is possible due to the current sources. Your circuitry appears different. There is no folded cascode which I would have expected to see at or above M44, so you are using some form of current mirror instead. I am don't know how this will work in practice and it is different from the X topology which I am very familiar with. My initial concern was before I had analyzed this portion of your schematic was more concerned with whether you could get balance in the current sources on bottom (i.e how well would they track). When I build my first unit, I went all out and degenerated all of 20 or so volts across the source resistor in order to get highly predictable current sources out of a FET unit. The problem with FET's is their high variability in Vgs which even with tight matching is "no match" against their BJT counterparts where you can rely on Vbe to be pretty darn on target.
So to cut to the chase, I don't fully understand what you are trying to accomplish and therefore it would be best for me to refrain from commenting further. I do not want to discourage you, so please do build and report back to us.
Serge,
The "original" X circuit is far removed from the Aleph-X circuitry. Aa far as number of transistors needed to generate your desired output power, there really is no clear cut answer. Mr Pass uses many more transistors than strictly necessary. Indeed from the datasheets, most amps can be built with single pairs (per balanced leg). Your design choices, particularly for Aleph type "Class A like" circuitry probably make it even more important to select the cooling capacity of the heatsinks first.
There is at least one separate Aleph-X thread where I have not been contributing so others if you post to relevant threads (this one is about X topology, not Aleph nor Aleph-X topology) you might get more appropriate answers or even find the design you are looking for.
Good luck, guys!
Petter