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
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.)
I was wondering about this 'crossing over' thing. I currently just send dac output to the amp. (Gustard x20 -> magtech) I spent a fair amount of time troubleshooting the USB output of the pc feeding the gustard. Finallly settled on a custom USB card driven by an external linear ps and the sound is good. Now adding a sub to this setup can be done at the speaker level or the line level.
1) I do not understand how adding a sub at the speaker level lightens Maggie 's load. It is a parallel electrical connection at the binding posts so the Maggie sees no change in voltage or frequencies presented to her.

2) a line level connection through a Y connector presents the same issue

3) a preamp w bass management and eq as well (emotiva?) seems the only way to lighten Maggie 's load. But I am concerned about adding another component in the chain with its a/d conversion, digital processing, and then d/a conversion. But I guess if I have a pc as the source I can just run Dirac on it for the eq. Which brings me back to the eq method. I am leaning towards rhythmic subs with the peq amp option.