Technically with a passive DI box you can reverse the signal, have not tried this personally myself though.
Regarding the X-amp, i have used radials passive ProRMP and from what i have read some people prefer either passive or active. Active could lead to earth hum from bad wiring but passive could lead to tone problems if it is not up all the way. Again, not saying these are facts, just some stuff i have read when looking into re-amping myself.
Its worth giving the JDI a go, and if it works, and you like the sound you get, why not