Do Passive Pre-Amps 'Limit' the Lower-Mids?

OK, I have what is probably a stupid question. I've been using passives for a long time now. McCormack TLC, Endler, Promitheus Ref 4, and now a Promitheus Signature. I like the TVC's a lot. I've recently been auditioning speakers, and I've had numerous systems come across with an unnatural level of dynamics. They just don't sound like any live music I have ever heard. And this is with my music, so it is not the recording. All the stuff I have auditioned has used an active pre, and I have found myself wanting to bring my own front end into the store so I can understand what the speakers actually sound like. Is it possible an active can be responsible for an effect like this?
I wouldn't mind trying a really good active sometime, but my recent experience has given me pause.

Thanks Clio.
I guess I'm also wondering if any one else has experienced this "too dynamic" phenomenon. I'd guess about half of the systems I've heard have been "too dynamic" in the sense of being quite unnatural, and I've heard this in more than one shop. Has anyone else heard anything like this?
Maybe it is as you say bad synergy, but really, can the brick and mortar shops be that bad at putting a system together?
On the other hand, I heard an Esoteric/BAT/Wilson system that was just wonderful. The only thing I've heard so far that was to my ears pretty much flawless.