Passlabs XA .5 vs Ayre MXR

I think the .5 is a "major" improvement if you have speakers with unsmooth impedance curves with dips below 4ohms - the .5 is better able to handle that, with a speaker that is "tube" friendly I can't imagine much if any difference as they don't need huge current to run their best, they are made to sound good with tubes (the XA are more like tubes in that sense than the .5 - the follow a voltage paradigm). Don't know abouth this warm/cold divide, the XA30.5 sounded true in terms of timbre. Ultimatelyu I prefer tubes with my speakers becuase I like the soundstaging effects caused by tube distortion (more 3D and layered to my ears).

Speaker match is critical, obviously Richard likes the Ayre for his speakers as he showed with them a few times, including RMAF last month. No doubt these are the two SS designers at the top of my list (and the Symphonic Line guy in Germany, and Richard Brown and BEL).

I suspect that both amps would be electrically compatible with any speakers assuming enough power, by match in this case I mean that Richard likes the way the Ayre makes his speakers sound; you could be pretty sure that the Ayre is a pretty good match with the Vandersteen's sound signature. That being said, I can't imagine the XA160.5 couldn't make most speakers dance as well. These are among the finest SS amps made IMHO and can't see why both would not work well. Since the Vandersteen's bass is self-powered, I can't imagine either amp being a problem. Really I think this is a toss up and is just a matter of taste - they are both great amps - I can see why you ask for help in deciding, but I'm not sure there is any defintive answer hear as neither one s*&^%ks. Not a bas position to be in.