Disregarding the physical characteristics between the 2.2 and 150's, what are the big sonic differences:
1) Sound stage dimensions, and center fill
2) Sense that harmonics are true (ie one big part to the musicality factor)
3) Midrange -- one of my favorite things about this particular Thiel
4) Dynamics -- can you feel the impression of the sonic texture more or less or maybe equal?
I have been interested in Pro Ac's for quite some time, and though I am very happy with the 2.2s (IMHO I honestly don't think that the 2.3 or 2.4 have add any extra value over the 2.2) I am at the point where I am willing to try something else.