Supplementing KEF Ref 3 METAs

I have the pre meta Ref 3’s. They were upgrades for pre meta R11’s. I found the Ref 3’s to have substantially tighter and lower bass than the larger R11’s. I ran them both full range. 
I have one Rythmik F12SE. With the Ref 3’s, the Rythmik high pass was reduced to 40hz to properly integrate as measured by REW. So it adds some, but substantially reduced value vs with the R11’s. Regardless, I believe the F12SE to be an excellent match for your KEF’s. 

@greatdivide71 Why would you connect the F12s to your KEF terminals?

I am also running a pair Rhythmic F12SE with my KEF R3 metas.  I use a SHD Studio to perform the system's bass integration.  It is like discovering my music collection all over again.