As far as I'm concerned, MQA is flawed. It's just a format designed to help entry-level digital systems sound reasonable or more analog-like. But it's lossy and it tricks the ears of the beginners into thinking it's better... It's not...
I'd love to hear one of those 625 S2's as I've heard only good things about them. I'm a long time fan of Jeff Rowland's designs (including their class D amps) even though I've moved to BAT and recently to Vitus.
I really liked what AQ Niagara 5000 and IsoTek Sigmas are doing with amps. I didn't find them to limit the dynamics of my BAT VK-655SE! Highly recommended!
Wow... pretty mixed opinions! I felt that Hurricane HC is very energetic yet full bodied and digging deep in the bass department... I've also found it to be quite transparent...
You've got a great system... looking at your signature! May you enjoy it in good health! I was wondering if you have any prior experience with other reclockers and/or USB galvanic isolation devices (UpTone, Intona, SOtM), etc.