I use Burson's first power amp (PP-100) with Gallo Stradas (87db) with their TR-3 sub. Using Audirvana, I've been pretty thrilled with the sound.. but always wonder how I can make it that little better.
Bugger about the hiss. I had a similar problem with the HA-160D. (Using shielded ICs didn't eliminate it).
But that hasnt been an issue with the Conductor. (I only hear the faintest hiss when the volume is on full on high gain mode (no music playing, obviously))
Hope Team Burson come through with a fix for you.
If you haven't Audirvana 1.5.5+ (now 1.5.7), I suggest you give it a whirl :-)