Subwoofer options for Magnepan with crossover betwen pre and amp?


I'd like to offload the bass below 50hz to a subwoofer through a crossover placed between pre amp and amp; believe this will (a) help with stabilizing the Prima Luna amp by eliminating low bass clipping (b) remedy the lack of weight in the low bass with Magnepan 1.7's. Has anyone found a combination they liked for around $2k? I've seen Vandersteen 2WQ's mentioned, I suppose separate amp/crossover TBD with Magnepan DWM panels are another path. My main concern is a clean merge of the subwoofer with the SQ of the Magnepans
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If you have the room, and are patient, another option is the bass panels of the old Magneplanar Tympani bass panels. Both the T-I and T-IV models consisted of three 16" wide x 6’ tall panels, two of which were for bass only, and they make great subs for modern Maggies! I say patient because they have become pretty desirable, more people looking for them than are selling them.
Just to throw another option into the mix, have you considered infrasonic generators? The Maggies are fast, so you want fast sub-bass which can keep up. Aside from possibly the Magico QSub 15, the Wilson Benesch Torus Infrasonic generator is the best ’subwoofer’ i’ve seen. My friend has a pair in his $500k system with a pair of Magico S7’s and they blend in seamlessly & work a treat, which is impressive considering the big price disparity to the Magico QSub 15. The Torus also comes with an outboard crossover/amplifier.
I am a big fan of the Vandy 2Wq.  I own a pair, but not using them with panel speakers.  I used them first with Vandersteen 1Cs, and now with Ohm Walsh 2000s.  They continue to delight and provide deep, full, tight, accurate bass, with a seemless blend with my mains.  I did upgrade to the HP-M5 (?) crossovers, which offered a real improvement in transparency and resolution over the basic in-line filters.
There is no one sub that can offer a smother in room bass response then
 a pair or even 2 pair.
The Vandersteen 2WQs have been great with Magnepans
 they hook up at speaker level and unload the main amp from heavy lifting in the bass, their unique hi pass allows the whole systems distortion to lower dramatically improving transparency and clarity.
 Best JohnnyR
Magnepan and Vandersteen dealer
Ignore Johhny's/audioconnection's advice at your own risk!  In my view, he's the best in the biz.  

(No affiliation with audioconnection--aside from being a customer.)