I have been using 4 small DIY subs for years. Not with a Meridian processor but it will work the same way.
It's a way to rid off most of the room modes, It sounds very clean and tight. I use a mixer (to add the lows from the closest small surrounds to the closest sub combined with LFE) and DSP per subwoofer.
The in room bass response from 17 - 150 hz was within 4dB.

This is an interesting read on the subject harman/multsubs_0.pdf