I replaced my Pass XA30.5 with the Luxman M-600a last night (used & broken in) so I'll share my impressions thus far. The first thing that struck me is how these amps are more alike than different so I think Faxer's "miles ahead" statement is overstating it, but I agree that the Luxman does have the upper hand in every area. I would describe them as having a family resemblance in sound, but the Luxman is more polished and refined.
It offers more detail, but in a somewhat subtle way that is not pronounced or exaggerated in any way. For lack of less cliche phrasing, it lets you hear deeper into the recording. For example, in The Temper Trap's "Love Lost" there is a pause prior to the second chorus which I always heard as complete silence, but the Luxman revealed to me that there is actually a very soft whispering sound before the dynamic burst into the chorus.
The M-600a has considerably better bass definition and weight, which is the Pass' relative weakness (though it does not do bass poorly), a little more tonal purity and density, and sweeter highs. It also provides more clarity and removes some very slight hash and haze that results in the XA30.5's softer sound. The M-600a has a slightly wider and deeper soundstage as well as better image focus and definition.
Bear in mind these differences are all noticeable but not huge, except maybe bass definition. I LOVE the Pass. It is an outstanding amp and a bargain for the high level of musical, natural, and realistic music it produces. I would say the amps play in the same league, but the Pass is a dependable, solid player whereas the Luxman is an All-Star. Everything the XA30.5 does very well the M-600a does a little better. It just makes the music even more realistic and hits you a little deeper in your soul.
