SPEAKERS, SPEAKERS AND MORE SPEAKERS.. BUT NEED BASS.?

Or possibly don't waste money buying modern stuff that will loose half its value the moment you walk out of the store with them :(.
Be patient and wait until a mint pair of TDL Reference Monitors become available. I promise you will not be disappointed. You won't be able to listen to them if you have loose bowels though. I'd forget sub-woofers, instruments of the devil.

 @audiokinesis  "The net benefits of not using a highpass filter were greater".  Hello, Duke.  You bring up an excellent and mostly overlooked point regarding subs and crossovers.

When I purchased my Coincident speakers, which consist of satellites and subwoofers, I could connect the subs to the sats using the subs' crossover, or not.  My experience mirrors yours exactly 

... 2 differenT pairs of Gershman Avante Garde for sale on Audiogon:

The RX-20 pair are older; either are a golden choice:

CHECK THEM OUT - READ THE REVIEWS ON THE INTERNET - CHOOSE/GET A PAIR OF THEM AND BE HAPPY!!!

My error: RX-20s on USaudiomart, the other pair on Audiogon...

Dear @audiokinesis :  The main reason to integrates a pair of self sealed ( not vented ) powered subs in true stereo fashion along any passive main speaker in a home audio system is to reduce IMD in the speaker/system and you can achieve that main target only through a high pass filter ( teflon cap. ) like the one @bdp24  advise.

As a fact that's why I'm doing inside my ML 20.6 monobloks.

You can read about that IMD main target along all other advantages that other gentlemans posted here:

https://forum.audiogon.com/discussions/do-you-think-you-need-a-subwoofer/post?postid=310058#310058 

According with a scientific JBL studies the ideal number of subs in a home system is four subs and at least two. The number of subs makes evenly the room/system bass frequency range response.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.