Using your known headphones as a baseline to remove variables was a prudent plan. Not using headphones, I wouldn’t have thought of it. I assume using them would provide a superb idea of detail retrieval, perhaps even better than speakers.
Years ago, I did something similar to remove variables. Prior to my SoundLab’s, when auditioning amplifiers at an out-State dealer, I took my CD Player to use with the Martin Logan speakers I owned and the dealer had, to try to create a similar baseline as you did with your headphones. From that audition, I ended up buying my first truly high-end amplifier, a Mark Levinson 336.
From reading threads here and elsewhere, I believe a Pass class A amplifier like your XA160.8 may prove to be a worthy replacement for my Atma-shpere’s. A distinct luxury and the best of both worlds may be having both amps on hand.
Because of a combination that you’re happy with, I can only assume that your XA160.8 has sufficient power to play your SoundLab’s at the SPL you prefer. That would be my only hesitation in considering the XA160.8. But my new SoundLab 845PX panels and backplates make the speakers a much easier load then when I had my first pair of M1 SoundLabs. So if you’re happy and with the XA160.8, my guess is that I would probably also be.
Speaking of happiness, did you audition a non Class A Pass with your SoundLab’s, like the X350.8? Also have you compared a XA-200.8 to your 160.8 with your SoundLab’s? When I auditioned the Atma-sphere MA-1’s against the MA-2’s, the latter had more gravitas for lack of a better description. But they had nothing resolution or enjoyment wise, that would cause me to plop down the much higher cost, let alone dealing with 40 (verses 28) output tubes. My former CAT JL3 amps had 32 6550’s later changed to KT120’s. A new mortgage on the house was needed to re-tube those bad boys (grin). But they were simply super sounding amps with the SoundLabs.
Speaking of Convergent Audio Technology, the newer CAT JL5 stereo amp at 120 W/Ch, would I assume, be a perfect competitor to my Atma-shpere’s and your Pass. The first CAT amp I tried with my old version non-PX, non-present blackplate, SoundLab M1’s was the JL1 mono. At only 100-Watts per channel, I couldn’t believe they would drive my SoundLab’s at the time. But at 190lbs. each, I begrudgingly drug them home anyway. Compared to my Mark Levinson 336 at 350W/Ch., I was floored and immediately recognized that the CAT’s wouldn’t be leaving my audio room. The CAT’s not only drove the SoundLab’s, they controlled them! The Parasound Halo’s I also took home with the CAT’s, handled the SoundLab’s much like my Levinson did, but for less money. In fact, they may have been better than the Levinson. However, I didn’t do a lengthy comparison using the Halo’s however, because the CAT’s were simply the CAT’s meow:-)