Custom L-350's upgrade?

Hi everyone, I bought these L350 custom speakers that are 2 15" one passive and one 136a, le85, and 077's. Unfortunatly someone glued the woofers in permantly so I am going to have to remove the front baffle and make my own. Doing this I am wondering about maybe adding an 8" midrange, I dont think I could fit a 10" midrange in but could squeeze an 8" Now this is a sealed system btw. Do you guys have any suggestions, would it even be worth while, would I notice the difference? If you guys think it would be a good idea then how should i add it to the crossovers. my current custom crossovers were made with
136a- 20-800hz
le85- 800-8500
077- 8500-21500

What do you guys think?
Other option is to ditch the pr15 passive radiators and add another 2235 or 136a and install ports. What do you think would be better sealed or is it worth porting and adding another active 15"? Thanks guys!