Threshold SA/3 to Pass Labs X250 comparison?

Anyone done a head-to head comparison of Threshold SA/3 to Pass Labs x250 or owned or auditioned both amps? I've owned a Threshold SA/3 for many years and am considering an upgrade to the Pass Labs X250 -- assuming it is an upgrade. I like the SA/3 but want a bigger, deeper, more transparent soundstage -- within my budget. I understand the x250 is more musical than the 350, is a big move up from the 150, and I just can't afford the .5 series.

Thanks for your feedback!

The rest of my system is:
Resolution Audio Opus 21 CD DAC/Transport (running direct to amp)
Mirage M3's (bi-wired)
Cardis Cables and interconnects