I should have been more clear, sorry
I do have a "surround" system going right now....
my other speakers are yet to be built (the Adire LCC & some Kit 8.1's for rears).
My TV speakers are currently doing "center channel duty", & I have some temporary rears as well.
You may have misunderstood my post though, I'm very pleased wit the actual bass output from my 281 towers. I just want the extra "lowend feeling", maybe I'm just used to feeing the bass a bit more sce I have a 12" Brahma in my truck.
I am hoping the Aura shakers will provide the extra experience.
Yes, they are 4 ohms, I was planning on wiring each pair in series for an 8 ohm load. I value my receiver & don't want to abuse it
As I am reading more & more into the huge manual, I *think*
I can program the #6 & 7 channels to use whatever input on the back, say Video1 stereo input, for example.
Now my idea was, if I used the normal sub-out, the 7200 lowpasses that signal, so the shakers should be ok.
Am I making sense? I sure hope I don't toast anything!

I get back from my buisness trip tomorrow, so I'll have to go through the onscreen menu & see what type of input the multi-room option will allow.
Thanks for the input!