I sounded flippant. Sorry about that. The XAs must be very attractive to Aleph owners. My experience is with the X amps. I am currently using the X600 on brutal speakers. The 600 runs class A to about 200 watts. Because of that, I have a pretty good idea what the XA would sound like. After all, the XA is a highly biased X. Compared to the lower powered X150, one that crosses to AB at 15 watts, the 600 was smoother, had greater depth, and more body.
I am sure your Aleph experience left you with a need for class A performance, while you express a desire for upgrading to newer electronics. The advantage of the Supersymmetry X electronics over the Aleph, is a purer signal, plus greater dynamics.
The X350 is biased to about 100 watts class A. Used, they can be found between 4 and 5 k. The 600 blocks can be found between 7 and 8k. Used XAs will be almost impossible to snag.
Good luck!