I definitely let them slam haha, but perhaps not as much as you and some others.. To clarify my other post though, the X00 doesn't really reach unsustainable levels for me. The bass on the SZ2K just keeps going where the X00 seems to just taper off or distort and I end up with overwhelming mids and treble...my definition of slamming only lasts me maybe 15-20 minutes tops before my ears will hurt and I'll have a headache for at least 24 hrs. after.
For quantitative measure, the threshold for me is about where my iCAN shuts off at max gain. Depends on the frequency, but the iCAN has trouble powering the really low frequencies to big levels. Looking forward to getting one of their more powerful offerings in the near future.
But overall, the sonic qualities of the X00 and ability to still produce copious amounts of sustainable bass make it the clear winner for me, especially since the price of a used one isn't too much more than an SZ2K.