couple of notes- the JBL's at the local Best Buy didn't seem to be finished very well.
be careful on the MB's.. they are all 4 ohm speakers, so be sure your receiver can drive them.. alot of today's stuff won't. the specs look really good, though.
if you are limited on the amount of time you want for a test, take the Trans-Siberian Orchestra's Christmas Eve and Other Stories.. song # 8 (Christmas Eve in Yugoslavia) has a very unique blend of flute work at the beginning, cello and base violin in the center, and some very fine high guitar work toward the end. it will quickly expose the pretenders.
if you have John Butcher's CD wishes (and everyone should), try song # 1 (Goodbye Saving Grace) for axe work and the title track for some very intricate acoustics.
if you want to test the HT, I'd recommend the A-10 napalm run in Courage Under Fire. The depth charge scene in U571 is another good standard. The depth charges test a sub and the left-right seperation, but the A-10 attack moves across the screen, showing how well the speakers follow movement.
remember, shopping is half the fun... then comes having, and then the best part of all, bragging....
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if cats can't do math, how can they always find the geometric center of a bed ?