when i changed my 28 y.o. amp (Hafler 500) for new QSC GX5, i tried comparative listening for a couple of weeks and never heard any difference in SQ.

the only reason i bought a pro amp is $$$;
same specs and quality as costly "audiophile" amps, for a fraction
of the price.

See: http://www.blu-ray.com/community/gallery.php?member=Gelli
or: Axiom Gallery