I have 4 of the cheapie auroras in my HT. Put two on each chair. I took a different approach from screwing them into the frame. In my case also, due to the construction of my chairs, if I were to screw them into the frame, you would feel the effect much more strongly through the arm rests, which would kill the effect.
I took some "zip ties" (you know, those plastic strap thingies that you use to secure wires together) and attached a zip tie to each of the 4 mounting holes, and secured them to the spring/supports for the seat cushion and seat back. This transmits the effect directly into your butt and back, and really enhances the effect. As long as you don't crank 'em up to high, your mind perceives the effect as serious bass. I had several people ask me "wow what kind of subwoofer do you have" not realizing that it was turned down at the time.
This is also a good thing if you have other people sleeping in the house. You can still get a good bass effect, without waking anyone. (or neighbors if you're in an apartment).
I found an old 100watt Radio Shack speaker/PA amp that works great for my shakers. I put the amp under an end table (hidden) where I can adjust it from one of the chairs. Runs off the sub output from the primary AMP.
TIP: Try running the input into the PHONO input. Yeah, I know it's not made for that and if you were using normal speakers it would sound distorted and awful... But we're going for tactile sensation, not sound... and the added "punch" the more sensitive input gives, gets more effect out of your amp.