Bass management--high/low pass filtering

A few days ago I posted to this forum seeking recommendations for a new subwoofer, and that discussion has turned out to be very enlightening, offering advice about subs and integrating them into my system. One reply mentioned the advantages of bass management for my main speakers (Ryan R-610 bookshelf speakers), but rather than sidetrack that discussion I thought I'd ask this separately:

It was suggested that I try cutting off the frequency response of the Ryans at 60 or 80Hz and letting the sub take over from there, thus relieving the mid/bass woofers of that substantial burden. On paper, this seems like a promising avenue to pursue, so I'm wondering if anybody has tried this and if there is a hardware device that can accomplish it. I'm certainly not an electrical engineer--far from it--so trying to design and build one is way beyond me. 

My integrated amp is a Modwright KWI200 and my previous sub (which is now dead and not repairable) was connected via speakon (speaker level) cable, though the Modwright does have a pre-out that can also be used to connect to a sub.

While pretty much all active subwoofers have adjustable low-pass filters, it appears that this would entail a high-pass filter somewhere in the chain. Is this something I can buy as an add-on? Couldn't find anything online, so I'm hoping that somebody may have some suggestions. Thanks.