I think your instinct is correct. Stay with the Ref 1's and Velodynes. If you really have an itch to do something that will take the system to a new level sell the SMS 1 and get a DEQX Premate. It has a far superior bass management system and full spectrum room control not just the bass. You are all digital to begin with so you will take a digital output off all your sources to the Premate which has four channels of DAC in it, one for each sub and each main speaker. This will also give you the ability to EQ your system any way you want. You will not need a preamp either so you can sell that to make up some of the cost.
Someone please talk me out of this
I use KEF Reference 1s supplemented by a pair of Velodyne HGS-15s controlled by a SMS-1 bass manager that provides acoustic room correction. I think the sound is superb even with large orchestrations since I raised the crossover of the subs from 40 to 80 Hz. BUT I think I’ve found a pair of KEF Reference 207/2s for $7200, and I’m very tempted. The preamp is an Ayre KX-5/20, amp VX-5/20, sources Roon via QX-5/20 and discs via DX-5 DSD. I previously used KEF 107/2s that I loved. but I suspect the combination of Ref. 1s and HGS-15s is superior.