Just wondering if anyone has done any upgrades or part replacements on a JBL M553 electronic crossover.

I"m using one with a pair of Tannoy SuperDual S250, each with dual JBL 2235s to support frequencies below 180 Hz.

In some ways I prefer the sound of the system with the M553 to the much higher-tech dbx DriveRack 4820 that I also use...

Which has got me wondering whether opamp or other upgrades could further improve performance. . .

Any tips or suggestions much appreciated!