Martin logan subs any comments?

I have owned the depth sub from martin logan for under a year and am happy, but wondering what others have found when comparing other subs to this one?
Something I learned in this crazy hobby is -- I don't know how much better it can get till I upgrade with the right stuff. Is the JL audio stuff that much better to justify making an upgrade?
A buddy of mine uses the ML Depth with his ML SL3s. He was pretty happy using the built in high pass filter. He bought an NHT X2 filter so that he could run balanced IC from his Pass Labs X1 preamp to his Parasound JC-1s. He thought this was a step in the right direction. His next change was an addition of a Velodyne SMS-1. This has convinced him once and for all of the importance of the room.

So I think the moral of the story is to address the room. Though it's clear from this: that the Depth will handle the lesser demands of music much better than HT. Below 95dB SPL and above 30Hz it's reasonable.
Get rid of the depth, there are subs that destroy it at the SAME price point. Doint buy into name brand. SVS alone is MORE musical, and the bass extension range and loudness will destroy it!

I had the logan descent, and my svs ultra/2 for $1k less new was better in every aspect!!!