I thought the X-sub was good above about 30Hz (we didn't get to run numbers on Ron's). With the bass boost turned down, it had good output and sounded good with music. Not as defined as I would like, but when you consider price, it was doing a great job. The amp is actually the most impressive thing about this sub, and I'd guess looking at the components, is probably about 60% of the total cost of the unit (if not more). The weak point being the driver.
I forgot to bring the polyfil that I have to try to stuff this guy a little bit when we put it back together to see if it would help any, because I think this guy would benefit from it (maybe 30% fill?). We tried stuffing the port also, and it actually made very little difference, which kind of surprised me.