Thanks again, mntngrown, for setting up the GTG. Just to give a little more feedback:
We compared the 210 flex mod sub vs the "regular" 110 sub that pairs with the 45. Not too surprisingly, the 46/210 sub was clear and balanced through the range, with a fullness and extra lowend heft as compared to just the 46 by itself.
The 46/regular sub (both cabs direct from amp) was bassier - a high bass/low mid hump as Mike correctly predicted here a couple months ago. BUT, to my ears, that extra bassiness gave a nice extra blast of oomph and punch without losing overall clarity. Different flavors.
Then we compared the 46/regular sub with the 46 daisy-chained from the regular sub with the sub's cross-over engaged (this cross-over switch sends the lows to the sub and anything above, say, 100 Hz, goes to the 46, and it's set at a lower crossover frequency than the 210 flex mod sub, for those who haven't been keeping up on this). I think we were all pretty surprised how similar it sounded to the 46/210 sub - again, balanced but with extra authority compared to the 46 alone. Not bad.
So, to my ears at least, the regular sub offers a couple of choices with the 46 which would probably be nice for all but the best-eared among us who want perfect balance between cabs/drivers. But I really like what either sub does for the 46 for those looking for a little more volume and authority from a single 46. Again, different flavors.
Thanks, DM