PS Audio BHK 300 mono VS Modwright KWA 150SE mono VS D'agostino Classic stereo

No experience here.

For your Thiel 3.7's, FWIW, going purely on the specs, in order:

(1) D'Agostino Classic Stereo
(2) PS Audio BHK 300 Mono
(3) Modwright KWA 150 SE

Thanks unsound, do you think the D'agostino classic amp could drive a pair of CS 7.2's just fine ?

No experience with PS Audio amps only power products. IME if you need anything their customer support is outstanding! 

No experience with PS Audio amps, but do have their P10 Power Plant, DirectStream DAC and PerfectWave transport and like gshepardbuster have found their support to be really excellent!

I believe PS Audio has a 30 day money back guarantee, if you purchase their products new, thru them or one of their authorized dealers.