"about the 2CE Sig. II, I didn't find the clarity and imaging I heard from typical British speakers"
My Sig IIs were somewhat veiled in the midrange at first (much like what Art Dudley wrote about in Stereophile). Break-in, set-up, and (especially) cables really opened up the midrange. The newest iteration is said to have a new midrange driver, the woven cone from the 5A. I haven't heard it but presume it has greater transparency.
Regarding imaging, I'm surprised by your comment because I find the Vandy's to throw as big of a soundstage as any speaker I've heard (that list includes stuff like TAD Ref Ones and Avalon Ascent) with stable, palpable images. Years ago, I owned Chartwell monitors and still have B&W DM12s in a secondary system. To my ears, the Sig IIs are better than those British montiors in every parameter I can think of. Never heard a ProAc or Harbeth, tho'.
Also, Ayre is a great match with Vandersteen.