i heard those Z6 components, i was not impressed at all. they were running off a 150x2 amp, and it definately sounded underpowered, no midbass at all. threw on a 400x2 amp, and they definately got louder, more pronounced midbass, but it still did not sound good, i prefered my HEX's over them.
this was in an avalanche, and the customer didnt like the Z6's either, so he ordered the utopias, sounded wonderful, total opposite of the Z6 and you dont need some ridiculously huge amp to run them. i prefer the boston pros over the Z6.