filters on speaker cables

I have a slightly long winded question on adding filters to my speaker cables to bleed of low frequencies. So is it possible to add a filter to each speaker cable to lessen to load on the amp when reproducing low frequencies? And if so what value,where do I get them, and how do you install them? I would like to add a stereo pair of quality subs to my system. I am using a Modwright KWI 200 integrated amp with Tyler Acoustics Woodmere II Speakers. I love the sound of the integrated but no way to add a crossover to the system as is. There are many here that say adding subs and lessening the load on the amp and main speakers has great results, so much so, that I really want to try it. So I am looking for another option without buying separates. Any advice is greatly