Pass Labs XA and XA.5

Has anyone any ideas on the difference (sonically) between the XA and XA.5 amps from Pass? I have the XA 60. I have had almost all of the Alephs, an x350 and an x350.5. The 350.5 was a big improvement on the x350 but I wonder about the XA.5. It is three gain stages instead of the two in the XA. A lot more power into lower impedences obviously. I am wondering if the first 60 watts of the XA.5 sounds better than the first 60 out of the XA. J fets are great but that is a lot of $ for four transistors. I assume the XA.5 is a step closer to the x.5 series. Nelson has come full circle and hit all the power requirements for each market. I know the XA sounds better than the Aleph 2's I had...which is saying a lot. But I think the Aleph 2 sounded a lot better than the OS which had three stages. Thoughts? and thanks
I've owned the Aleph 3, 5 and 2 and the XA160, XA100.5 and now the XA160.5. I have never owned the X or X.5 series. You can read my review of the XA100.5 on this site. I think the XA.5 are the best amps that Pass has designed.

Regarding your question about the first 60 watts: I replaced the XA160 with the XA100.5 and probably listened most of the time within the same 60 watts into 8 ohms on the same speakers because I never saw the needles move. However, the XA100.5 sounded much better and more powerful ie effortless. There was an ease to the sound. Other aspects also improved as described in the review. It was a huge improvement. My new speakers need even more power, so I moved up to the XA160.5. I can't comment on the effect of the number of stages. Hope that helps.
I owned the X250 and recently moved to the XA60.5s, but can't comment on the XA series. The XA60.5s are a big step up from the X250. All aspects improved, soundstage, midrange and bass authority. I'm running ML CLS IIz and the XA60.5 are a great match.