Bass management--high/low pass filtering

Once again, this has been quite the education. Thanks to all for your suggestions and input on the subject. In the end, this seems like too many hoops to jump through to get the high-pass filtering to work in my system, and my previous experience with a sub (my late, lamented REL S/2) tells me that, as interesting as it would be to try, it's just not going to be practical. In particular, I'm not willing to invest $3K plus in JL Audio's CR-1 just to see what would happen. 

My room and my setup preclude using a pair of subs. I can only fit one in that space, and the REL sub filled things in admirably. For our listening tastes, at the volumes we are comfortable with, one sub is more than adequate. 

Still, I've learned quite a bit from all your responses, so again, thanks!

Every room, and every system is different. My take is don't buy new stuff until you need it. Also what is the problem you are trying to solve for? Like are you missing bass, or are you missing deep bass?

Run the mains full spread, add the sub, adjust it to fit your mains. Then live with it for a few weeks, it will take several adjustments to get right. From there, figure out if you want to cross over your main speakers or not. 

My HT has everything crossed over, my mains are at 60hz, subs are also at 60hz, it works well there. Plenty of bass, clean sound.

The 2ch has the mains running full, sub crossed at 40hz. Tried all the hi-pass and low-pass settings. It was just missing something. Lost body and tone on my mains. Sounded almost hollow in spots. After weeks of messing with it, went no crossover on the mains, and 40hz on the sub, the light just clicked, this is correct. 

My other half felt the same way. Was listing, she walked in, looked at me, and said "this sounds great". That was all I need to hear about my settings.

@cooper52 the crossovers I made, with some help from GR Research regarding the schematics, caps and resistor values, cost me about $250 in total, using high quality components and about two hours of my time. It’s also quite a fun DIY project, and far from a $3,500 trial investment. Let me know if you are interested in more details.

One of the best discussions on topic I've read here.  When I posed this question to Verity Audio they agreed with most of you to leave main speaker alone and adjust your sub. Thanks all.

This very issue -- how to apportion audio frequencies above the desired cut-off point to the mains, and leave the rest to the subs -- defined my "sub journey" for years until I finally put some time & $$ into a solution:

It’s an electronic crossover. Mine is a single-ended, variable crossover point model from Marchand, a designer well known for high quality crossovers. I bought this one used for ~$500, and it has worked flawlessly for years. I run the output of the preamp to the input of the crossover, which splits the frequencies into 2 output pairs:

• High pass: Frequencies above the crossover point I chose, 75 Hz, go via RCA IC to the class D monoblocks (bel canto 600Ms) that drive Harbeth 30.1s in a nearfield/desktop configuration (strange but true)
• Low pass: Frequencies below 75 Hz go vis a 2nd RCA IC to the JL Audio e110 sub, in which I have the internal crossover bypassed

This crossover has trim pots for each channel to adjust the output of the crossover in +/- 1 dB steps. Once that’s set, all volume control is done by the preamp.

The Marchand uses 24 dB/octave crossover slopes, which work quite well in my desktop setup with a variety of speakers. This component is very transparent: I’ve compared the sound with direct wiring through the amps to the speakers (no sub) vs wiring through the crossover (also no sub). I can’t hear a diffrerence.

Before using an electronic crossover, everything I did was stumble, fumble, audiibly inadequate. This crossover instantly made the problem go away.