@imdoc , I think you are crossing over too low and the 3rd order crossover (correct me if I'm wrong) is a bit extreme. I would use something less drastic, like a 1st order crossover (-6db) starting at 70-80hz. If you have a well made powered sub, it should integrate and provide you with the bass you are looking for.
Not to beat a dead horse, that is why the Vandersteen crossover and subs do so well in terms of integration.
@akg_ca , If I, or 98% of the Audiogon readers could afford a $10K sub, then, yes, it might make a difference, but considering the OP has a pair of not quite current Maggies (and I wish I had 'em), I doubt he/she would entertain a pair of ATC C1's.
For comparison, I have an office system with a pair of Hsu VTF-1's paired with Zu Omen bookshelves. The Hsu, in no way compete with a pair of Vandy subs (which I used with a pair of Zu Union). I was blown away when I played music on them with my Atma's. So, using your Janis subs would kind of be like using my Hsu's, but YMMV.
B