I dunno Change, the M50X I'm sure is a banger, but I find them a bit too big for portable use, and your 1540 is sure to blow them away otherwise...
And yes, 1.5watt at 32ohm is Magni 2 Uber type power. That's damn good,80mw at 600ohm... that's E9 level, which is okay for sensitive 600ohm, but not gonna give headroom for the stuff with voltage swings. I was hoping for like 120mw @ 600ohm.
Still, I can live with that sort of power, especially if i have an alternate amp if I ever have 600ohm cans that don't play nice with it (which I'm sure isn't many anyways).
Now, I don't think Evs answered this, but how would one transfer SBX to ANOTHER amp? i doubt the analog line out does this, so I assume you'd have to go the old school route of amping through the headphone jack? I do believe the speaker out can have it's own SBX type of processing, but that's not headphone related. I guess a cheap DAC like a Fiio D03K with your own amp is fine, as apparently the X7 does pass SBX to the optical out.
As others pointed out and as I tested myself, the RCA Line Out does carry SBX processing with it, though it does not seem to bypass the X7's amplifier [the X7's volume knob still affected volume]. Unless one of the SBX settings in the control panel changes that,