Cutting below 80 HZ on my mains, so subwoofers handle deep bass?

A lot depends on the speaker's crossover as well as the drivers.
I think overlapping the frequencies, as pts suggests, will result in less accurate reproduction.

Some things said here are inaccurate.

First, my experience is that the subwoofer settings are not "brick wall" filters and allow a good bit of transmission of frequencies above the setting, which may or may not be accurate anyway.

Second, neither are the crossovers in the speakers "brick wall" drop-offs at the rated frequencies, rather they continue to generate sound at lower frequencies on a modest rolloff of output as the frequency drops.

I have found that it is necessary to set the crossover frequency of my REL subs far below what is notionally indicated to avoid bass bloat. Going higher is a step in the wrong direction, IME.

Third, subwoofers integrate better with full-range speakers when they are felt and not heard. The 30hz and lower frequencies from the sub(s) generate sound pressure that loads the room, giving a perception of greater bass weight and also better soundstaging.

Dave

The timing of this latest thread is perfect. I just purchased (on the way) Modwright LS36.5 linestage with a custom modification.  On my request to integrate a sub in a two channel setup, the wonderful folks at Mod configured the unit's only XLR input as a second pair of fully balanced XLR output.  A bit of sacrifice with one less input, but I gained a pair of fully balanced outputs, wired in parallel to drive my awesome JL Audio F212v2.  Until now, I used this sub exclusively with my HT setup. 

Since LS36.5 don't have a internal crossover for sub, I am hoping to tame the 'beast' with its internal crossover. My main speakers are 800D2 which produce adequate bass on most tracks but at times I miss that deep bass on some of my favorite tracks. 

@dlcockrum,  I agree with your comment.
"Third, subwoofers integrate better with full-range speakers when they are felt and not heard".

That is a super preamp, lalitk. Fine sub too. Congrats.

Dan Wright know his stuff. ModWright equipment is not cheap, but worth the cost and then some.

Dave

PTS,
I am still wiring my GR Research/Rythmik DIY sub project, so can't answer the question about the resulting sound. I am using an in-line filter to roll off my amps at about 48Hz just to my main speakers. My main speakers also go down to 30Hz. The filter was built by Danny at GR Research specifically for my application. Think about contacting Danny, because he knows his stuff.
Kenny