Have a look at mracoustat 1+1 s in the members systems in the community section. Is that the kind of improvement you are looking for ?
The same gentleman who did this job is actually rebuilding my Acoustat 3s into 2+2 s and I saw the new woodframe this last weekend. Astounding ! Layers of thicker plywood in replacement of original press wood. Much heavier for optimum rigidity. A shame to cover them with the sox. As per previous posts, the electronics can be rehauled and replaced with better parts, wire changed for silver or better quality, the membranes soaked and cleaned to renew their flexibility. Cell heads wiring stripped and soldiered for better dynamics. Heard the results of the process on his own pair of 6's. Oooooooohhhhhh my ......