JL Audio Fathom

If you haven't already, perform the subwoofer crawl and map your rooms two loudest standing wave bass modes. Position the ML 1100X's in those modes then recalibrating them. Despite the level of noticeable improvement at least you'll know that rooms optimum sub locations, forever.

The cost of custom length subwoofer interconnects from say, Blue Jeans or Monoprice Cable are quite economical. Try and maintain the same VAC supply to avoid grounding issues.

A -6dB  'Sub-Bass' speaker is not a subwoofer regardless of where its manufactured.  

I haven't been without subwoofers since the sixties.

After giving away my early Technics SL 1200 for a belt driven Well Tempered Classic I experienced that Basis Audio's A.J. Conti was defiantly onto turntable drive belt irregularities and aging. 

I missed my SL's drive power and torque from day one. I should mention I've been conformationally swayed by Oswalds Mills Audio's Jonathan Weiss direct drive philosophy. After over a decade without an audio purchase I'm currently squirreling away for an affordable Technics SL-1200G-S.