Years ago, I lived in Hope, AR and my father was a construction contractor.  He once did a remodel for Bob Moers, the president of Klipsch.  In the corners, where the Khorns were to be placed, he built a solid 3-4 feet of 2x4s out from the corner for bass reflection.  Kind of like your idea, but taken to the max.  Not sure how this would play out in terms of transmission THROUGH the lumber to other parts of the house, but I imagine it helped as far as getting the most bass extension from the folded horn. 

I edited my post above and changed out the image.   I had the wrong transformer model on there.   Mike, it is the stock Klipsch K-691. XO is DBX Venu360 10" B&C in a custom box ported about 70 Hz https://www.bcspeakers.com/en/products/lf-driver/10-0/8/10nw76-8   Subs are lab 12s in sealed box  

In the first post, there's a link to a thread showing photos.  

Those are in fabuluos shape.  Some of the nicest that I have seen.  If I was within realistic driving distance I'd make an offer.

A zobel circuit is more for use in a subwoofer environment not a woofer.  It most likely wont make any positive difference at all.  

JC… I really like the small speaker system with the K510…!!!   What driver are you using on the K510..?

I agree with JC and highly recommend the Jensen ISO-MAX units and use them in my systems.     FYI …. Jensen recommends the use of their PI (Input Transformer designs) whenever you have the option over their PO (Output Transformer designs). The Pl-2XX with input type transforms will give better performance than the PO-2XX unless you absolutely need to run an output transformer type.   Some info for anyone interested…        

You already know your room setup is not the ideal situation you see posted everywhere.  It may be difficult to get an educated recommendation. You may want to find a dealer(s) who has a liberal cheap/free return policy and buy the 600m ii's and the 502's.  Try both and return the losers.  

Insulating your floor and interior walls with mineral wool (Roxul Saf-N-Sound for example) will reduce the sound outside the room and help the bass inside the listening room. Also, you should read up about techniques for using mass loaded vinyl or applying something like Green Glue and a second layer of sheetrock.

I have never been disappointed in any Klipsch speaker Pretty much depends on your Budget.    I like my KlF 30 as much as my KH