Bought a house that the previous owner left Martin Logan speakers in the living room.  The current setup has the pictured Martin Logan Script speakers for the rear surrounds, and a Reel RSW-12 subwoofer.  I have a set Definitive Technology BP-8060ST’s that I am not using.  The DT towers also have built in, powered subs.  Should I use those as rear surrounds, and have both subs, or stick with the current setup?  Would the DT's be an improvement on the Martin Logan's?  I have no idea how old the Martin Logan's are.

From what I have heard, ML electrostatics are not great for theatre applications since they are very directional (very small sweet spot). It may not be bad if you don't have a big audience. If it's just you, get some ML for mains and keep the Scripts as surround... and get a new sub.

I've only ever heard MLs with music, but was quite impressed when I did. If I had spare space and some coin, I'd love to have a pair.

I had(have in storage) a ML surround system. Like the other poster said, they are very directional. They also do their best when they are out from the wall some. I basically set mine up for me and eff everyone else in the room hahaha, but that's because they still are so awesome sounding that it blew away what most people are used to. I have a big tube SV subwoofer with mine. That made a huge difference, not forcing the ML's to do any low end stuff.

It's been a long time since I tried them but back in the day the Def Techs were more punchy. Great for a Michael Bay explosionfest but musically they were not nearly as good.