Vandersteen

Very very unusual situation .......

What is the rest of your system? Sounds like the new VANDY speakers are an extremely poor mismatch with the rest of your particular gear.
system synergy matters --big time -- and one size does not fit all.

When you say they " fall to pieces..." , can you elaborate please? 

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.