Vandersteen

What speakers were you using previously in this same system where this did not occur, and what equipment are you currently using?

I am not understand what falls to pieces means.  Symphonic works could be the way your source and preamp send the signal, same for rock.  

The Sigs will do justice to some fine quality gear so the point-of-no-returns is likely elsewhere in your system. Vandersteens are very sensitive to toe in, tilt, and distance from walls but "falls to pieces" on complex works sounds more like a speaker control (signal) problem as noted above.

I've been listening to mostly hard rock and the blues through my 3A Sigs for the last 5 years.  In no way are these speakers deficient while playing that music.  You received some good insight in the last 4 posts.  

I've heard the 3a and Treo ct many times and they are absolutely fantastic. They do justice with all types of music especially complex classicals and rock. Then again, the source and amp was all Ayre acoustics.  I don't think it's the speakers.  Tell us what components your using and the type of speaker wires.