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Just as an FYI you need to turn the bass up on these Bose to really make them work.
I was just playing around with the settings, and yeah I noticed that. Bass was at the ~30% mark and it made a big difference just bumping it up to 50%. Turning the bass all the way down sounds the same as unplugging the sub (that wire I circled above is indeed the sub connector).
As for hardpoints there are 3-4 ~3/16" studs that seem to be welded to the body.
I've decided to leave the sub alone for now.
I wonder if your's is blown. I have mine turned up almost all the way and it sounds great in there.