I have the Aleph 4's which are a stereo version of the Aleph 2's. I corroborate those who say that the Aleph
amps are some of the finest ever made. They are extremely neutral, deliver tremendous detail in the highs while always sounding natural and unforced. Even the most minory colorations which I find in my system are always proved to exist elsewhere, not in the Aleph 4's. I use them with the inefficient, 6 ohm Vandersteen 3A Signature in a romm which is 22'x12'x8' and which is open to adjoining spaces. There is no bass problem. Bass is extremely deep and will do any pipe organ recording justice. This amp can rattle floors and windows if you are into that. What it doesn't do is give you the ultimate bass slam. The bass is not super-tight and punchy, but who cares! It is a wonderful amp in every respect. I have heard the Pass X series (X350 and X250). In my opinion, they don't compare for naturalness and for absence of all electronic artifact. Sorry Pass Labs, but that is my opinion. The fact that they developed the super-expensive XA series, followed by the X+ series in order to bring the sound of the Aleph to the X series would suggest that someone was not completely satisfied. I say just save your money and buy an Aleph. From some of the posts here, you might want to stick with the more powerful Alephs. I have heard the Aleph 3, the Aleph 4 and the 1.2 (200W monoblock). The 3 did sound a little underpowered in certain situations, but it is also a wonderful amp.