Stacking

It is hard to guess what will happen.  For one thing, you will now be seated much lower with respect to the height of the drivers, particularly, the midrange and tweeter.  You might have to angle the speaker downward to restore the same axis to get the right frequency balance and timing of sound arrivals from these drivers.  The woofer of the Klipsch is now higher off the floor and will be loaded differently and it will be delivering a different sound.  The path of the sound from the various drivers to the floor and then bouncing up to your ears will be lengthened, and this will affect how that sound and the direct sound from the speaker will interact.  The floor-bounce effect, and sometimes ceiling bounce effects are figured into the design and voicing of speakers; some manufacturers even figure this into crossover design.

You will just have to experiment and perhaps change the placement of speakers and/or the listening position and mess around with other aspects of system tuning to get things right as would be the case with any major change like this.  It

probably can be made to work.

I would think the vibrations transmitted from the sub would have a negative effect on the speakers.  Maybe build some sort of stand to isolate the speaker from sub.

@larryi , I'm using the altec 311/60 & Fostex 925 horns. So I can dial in per say the directions of the horns.

@abnerjack That's the reason of my post.

 Thanks 

Yes, negative effect(s).  Perhaps too numerous and/or unknown to list here.  To include possible instability of a large objects.  Best of luck on a viable solution.

I hear people have been having success in putting their subs behind their listening position. Just a thought.💭