It is a dramatic change to go to Mills Resistors, Goertz foil air core inductors (woofer circuit inductors), and Solen Fast Caps. Plenty of room to upgrade crossovers. Upgrade wiring to braided 14 awg except woofer and midwoofer, use heavy braid monster speaker cable. Of course, convert to biamp the two sections. You will find many resources for crossover changes online. I also have a crossover schematic if you do not find one.
A Scanspeak D2010 (corrected for ohms with a resistor) takes the place of the supertweeter and tweeter while a Hi VI DMN-A 2" cupped Midrange replaces the midrange. A nice Scanspeak Revelator takes the place of the mid-woofer and same inverted AR woofer main. Beautiful sound experience, just keep the speaker impedence correct and follow crossover mod to change tweeter circuit from supertweet + tweeter to 1 D2010 each.
I don't use stands, you need them to be on the floor to gain a low frequency advantage, very inefficient woofer.
They say to also remove the back metal shield too, but I have tried it both ways and as long as it's attached well with foam gasket there will be no noticible advantage. All of the above section speakers have a back carpet like covering (original covering) and the speaker does not rely on backfed sound.
Some would say that the speaker should be left original but I say why not improve on a great design with the latest enhancements in drivers and discrete components.
Wish I could post some pics here.
Good luck!
Reliaserv