I have a FMR RNLA that I love running stuff through before it goes into the Octatrack
I've been tempted by the JoeMeek ThreeQ to use as a channel strip for a mic before going into the OT.
Only outboard effect I own is the RNLA though hehe. Well, and my Octatrack and Monomachine. Very nice multi-fx if I do say so myself
And I can use the OP-1 as a mono effect with stereo output. Sadly the input sums to mono for the built-in four track.
But the RNLA is the only dedicated one >.>