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

Gryphon hasn't had a US presence in some time, I knew they were pricey, but just not how pricey. I can certainly understand your position. I've always like those Krells with Thiels. But, hey, it's your money. 

I'm familiar with D'Agostino Momentum stereo and it should drive  Thiel 3.7 based on specifications.

You should add Hegel H30 to your list.  I have one and is superb.  Again, base on spec it should the Thiel 3.7.   There are many professional reviews available online that describes the SQ accurately.

Thiel is terrific,
You have assembled a very worthy list of amplifiers.  I've heard the D' Agostino and the Ypsilon amplifiers on 4 occasions between the RMAF and CES. Show conditions no doubt but in good rooms that were very well setup on each occasion. Sometimes you can get a feel for the brand's "house sound" generally speaking. 

The Ypsilon is the more impressive in my opinion.  It comes across as more natural, musically involving and ultimately more interesting and captivating compared with what I heard from the D' Agostino demonstrations.  Ypsilon products consistently sound exceptionally well when ever I've heard them. 

You're planing to audition these various amplifiers which is near mandatory at this elevated level.  Obviously hearing them driving your Thiele is the ideal scenario.  I look forward to your listening impressions. 
Charles 

Well yes since the Ypsilon Aelius ll is in first position in my short list, the distributor has arranged me a home demo on my system with a Nagra Jazz preamp since he still didn't receive his PST-100 MKll linestage yet.
I assume Ypsilon gear being way above Aesthetix gear.
I already auditioned the Hegel H30 which gave very goog results on the CS 3.7
knghifi how did you like the D'agostino classic amp ? does it have a very refined sound presentation ?

That's an intriguing pairing of the Negra and Ypsilon, I bet it'll sound gorgeous.  Home auditions aren't always possible to arrange, it good that you have an accommodating distributor.  I am curious to read your listening impressions of the Ypsilon in your system and how it compares to the other candidates. I've heard the PST 100 and thought it was superb, natural the antithesis of electronic hifi sound character. An expensive brand but at least they sound quite good. 
Charles