Yes it is

Quite different from the Mark V and DR. I feel the JP sits perfectly with the Roadster (similar to the DR) and Mark V. Not exactly like driving both Mark V and Roadster (or in your case the DR) together but it is hard to beat the JP in terms of the raw power it has.
Blending the Mark V with a Dual Recto is a rewarding experience. You may even like it. I have both the Lehle P-Split and the "little Dual amp switcher". Both have the isolation transformer. P-slit does not require power but the dual amp switcher does. OI got both so I can combine three amps. Having the Dual amp switcher allows you to either run stereo effects or select one, other or both. That is something worth while trying out and it cost far less than another amp. What is cool about the P-split, put it in the loop and used the isolated output to slave another amp, or just use it on the front end. the dual amp switcher can make noise depending on environment but most of the time it is quiet. There may be other types out there but you should look for one that has a transformer isolated output on one channel to avoid the ground noise which can be tricky to remove especially when one amp is on standby. Just run a stereo effect pedal in bypass mode and you will hear what I mean. The isolated splitter or switcher eliminates the associated noise when running two amps in parallel.