Kim help! Is this going to improve

I have a new MM100 but it was a display model at the local audio store. I am driving it with a MTX blue thunder pro pushing 412 rms @ 80hz and below. It has about 5 hours on it from me but I have no idea how many from before I bought it or if it was damaged from never being broken in correctly. It has a good amount of bass and SPL but sounds like a speaker more than the song it's playing, even at low volume. Some notes sound good but most have that plastic speaker sound like a really cheap sub would have. I bought a Polk because I thought they had some type of cone that was quiet like a paper woofer but stiffer. The Dx speakers are suppost to be"uncolored' and not have cone resonance, and I thought the MM was just a souped up Dx. Should I just sell it and get a Dx or will it quiet down after 40 hrs. I've tried a different amp and even a home stereo and it sounds the same. The box is perfect .66 with 1lb fill and sealed completely. Thanks