ModWright Products

I have the Tryst headphone amp and love it. Dan is good people too. I know it's not what you asked but another data point.

My only experience is with the older Modwright upgrades, which were all very positive. Had a Transporter way back in the day that gave years of enjoyment. Later had an Oppo 95 which was also great. 

Never tried the amps but I can imagine they are well done based on what I've seen from Dan's upgrade packages. If there's a "house sound" I would call it smooth and natural. Detail is really good but not in your face, and everything just seems believable instead of artificial (which is how the Oppo sort of sounded prior to upgrades). 

Modwright is a very balanced sound, not unlike Pass Labs in general. 
 

I think you’d be moving sideways at best by switching from Pass Labs to Modwright, and if your Pass Labs amplifier is Class A vs Class A/B, then it would be even more pronounced.