I'm trying to figure out what you mean by "congested". Is it that the sound is not analytical enough, or does it seem as if the speakers are overloading, i.e. that they can't handle passages of loud and/or complex music? Or??
The VA Beethoven Baby Grands are my second-favorite speaker, and I've heard them handle Mahler with aplomb. Haven't heard the Mozarts, but I wouldn't expect them not to be up to the job.
To track down the problem you need to do a good deal of experimentation, with placement, amplification, and possibly speakers, swopping in and out components. This is a lot of work! If it finally comes down to speakers, and you still don't like the Mozarts, wondering if you'd be happier with something like Vandersteen, PSB or Focal.