So after a little more reading, yes, I see that a MiniDSP and REW can work together to improve a speaker's (with a passive crossover) in-room performance. Much of what I read was about improving/smoothing in-room bass response including how to integrate one or more subwoofers. Is bass were products like a MiniDSP have the most impact or can they "smooth" the response at higher frequencies to good effect?
With regards to my Ottavo they are much too nice a speaker to re-engineer. If the work was simple (e.g. disconnect the woofers from the crossover so they could be hooked up to an amp/dsp) and easily reversible maybe, but I wouldn't make wholesale and permanent changes. A minidsp hd and a mic are pretty low cost way to try and improve in-room performance.