Subwoofers to run rears and support rear speakers?

Well, my one first question is, can you tell where the subs are? If so, you have other issues first.

If not then sure, this is a hobby and no reason not to, except excess. :)

Apparently, more subs are better. Look up 'subwoofer swarm.'

The two existing subs do blend in at present system setup.  When the room is under pressure I feel the rear speakers Although good and powered by Luxman mx10 in stereo have minimal impact 

the two fronts and center all have their own Luxman mx10 in bridge mode

Thank you will check our subwoofer swarm!