Hello! I too use a Kingsley Maiden D in front of a C.A.B. M+ as the basis for my travel rig. Simon at Kingsley is a stellar human being and spoke with me for a while to help me decide which pre-amp I wanted. I know the OP likely doesn't care anymore since his question is a year and a half old, but I'll offer a couple of thoughts if others come upon this in a search. As I understand it, the Constable is indeed a lower distortion pedal, as the JTM-45 it is based off of got a lot of its distortion from the pre-amp overdriving the phase inverter tube of the power amp section. So on its own the Constable will have some distortion (more than the Maiden for instance), but not a lot. If you want the full "Plexi" overdrive tone you would want to add the Kingsley Hatchet after the Constable. That having been said, I use an EP booster running at 18 Volts before the Maiden D to push it in to overdrive and it gets a glorious tone. All the Kingsley preamps are capable of very large output to drive a power amp, but as @Dilan - Two notes said, the C.A.B M+ has 3 input level options to make sure that you will not clip it, so you can experiment with different combinations of output level on the Kingsley, input level on the C.A.B. M+, bypassing the M+ Preamp, etc...