BigX5er: Thanks for the detailed post and the feedback! I will pass your notes on to our tech / instruction guy and let him make adjustments as needed. If you would like assistance, please call us: 404.963.8857. We are happy to give tips and pointers on this stuff!
Also, keep your eyes peeled for a single 8" drop-in subwoofer system that we have in development for the X5's! Goes in the factory location.
That should be on the market in about 3 months or so is my guess.
Josh4.6: The speaker size difference does change the dynamics of the sound, but it's more a product of the way the driver itself behaves. The MB Quarts produce tighter, more accurate midbass, which gives the impression of less bass response even though it's more true to the music that's been recorded.