Well the good news is you have the best crossover on the planet made by Nelson to fit right in with your pre and amp the XRV-1. Start with that and also I have heard the newest version of the JL's and their DARO room eq is supposed to be the cats meow according to Nyal Mellor at Acoustic Frontiers. Talk with Nyal he is one of the best acoustic guys out there for doing what you are trying to do. He knows his stuff.
Also, I totally get the last 5 to 10 hz and the benefits of reducing your load on your main amps, etc. etc. . Read the user manual for the Pass XRV-1. Nelson talks a lot about the benefits of your pursuit. It goes well beyond the improvements of the last 5 hz.