Rob,
What many people who decide to upgrade the crossover do is build another one from scratch and save the original for resale. The original is a fairly basic 12db/octave crossover, nothing very complicated at all. Most folks recommend at least replacing the capacitors in the original, especially if the sound is suffering ill effects, as you say your's is. (Can you give us a more detailed explanation of exactly what you are hearing?)
One of the other Altec guys can correct me if I'm wrong, but I think your crossover may be one of those whose components are sealed in a tar-like substance that makes capacitor replacement rather difficult. You will be able to confirm whether this is correct once you open it up. If the sealer is not there, then it's simply a matter of replacing the capacitors with ones of like value. The caps are available from many sources, such as Parts Express. It's also very important to clean the inside of the horn attenuator (L-pad, level control, whatever one wishes to call it) with DeOxit cleaner. Sometimes it's possible to restore proper order by simply moving the knob from one extreme to the other a dozen times or so. They have a tendency to corrode at the contacts inside.
If the crossover is sealed, and you want to avoid the hassle of dealing with the sealer, it's a simple matter to duplicate the original with new components. You will need only to read the very simple schematic for that crossover, available on numerous sites, including this one and the Altec Users Board (
http://www.hostboard.com/forums/f700...ers-board.html ). Speaking of which, you may want to add your post and pictures to that sight, too. Many, many excellent and very helpful Altec specialists on that site with much, much more knowledge than I. If you have trouble finding a link to your specific crossover schematic, let us know and we'll find it for you.
You have some very nice speakers there, and they will be a fun and rewarding project. Once you have them dialed back in to proper specs, you will then be able to do some serious listening and determine if the "Altec sound" is for you. Some people love the Valencias, others not so much. One thing for certain, if it turns out that you don't care for them, there will be a ready market for resale.
Keep us informed with your progress. And more pics, of course!!!
GeeDeeEmm