Undoubtedly unsound will offer wise advice/suggestions regarding powering the 3.7's appropriately; his past advice regarding my former 3.5's was useful and utilized. Toward that end I have to once again offer my opinion on Pass Labs - if the cost is in your wheelhouse. Right now there's an X250 up for grabs here for $2500 - pretty much the same amount I paid for my two, on separate occasions, X150.5's. I believe the X250 is 250 into 8ohms, 450-500 into 4ohms. Pass was by far and away the most neutral or colorless amplifier I've owned to date, IMHO a perfect match for Thiel loudspeakers which share the same sonic descriptions - colorless, neutral, accurate.
Per unsound's spot-on remarks, the 3.5's were/are possibly the easiest Thiel model to drive without stressing the amp, 300 watts into 4 ohms and I never stressed a hair remaining on me head.
Funny how we evolve our systems around these excellent speakers, ain't it?