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

Thieliste, 
For all I know the CH Precision "could" be a better match with your Thiels than the Ypsilon.  My comments were based on hearing these two brands 3 or 4 times at shows in of course separate rooms rather than direct comparison in the same system.  Overall impression is that the Ypsilon consistently struck me as the more natural sounding.  In your system this may or may not be the case. I'm looking forward to your audition comments. 
Charles 

Do you think Ypsilon might be too transparent for the already very transparent CS 3.7s ?

No, I don’t accept the premise that you can have too much "true" transparency. I do believe that you can have too much brightness and tilted up high frequency region emphasis  that some may interpret as transparency.
Charles

I don’t accept the premise that you can have too much "true" transparency.

I agree with Charles.  I just received my Metrum Pavane DAC back from The Netherlands after being upgraded with their Transient  DAC TWO modules that are also used in their Adagio.  The transparency is exceptional and the result is an analog-like relaxed musicality - transparent, resolving, nuanced but very natural sounding....go figure.

Yes that's what i meant too much brightness.
I guess the only way to know is to try out.
One thing that is sure is that the Aelius monos will lack bass slam compared to a CH amp.
The midrange should be a little sweater and magical with the Ypsilons.