Mrmky,
GR Research is where you can find No Rez and upgrade parts.
www.gr-research.com
If you can't find what you are looking for on the website, email Danny at info@GR-Research.com.
You can just replace the caps, replace the caps and resistors, or if you really want to get into it you can replace the entire crossover network including caps, resistors and inductors. If you go this route you would point-to-point wire the crossover networks. You can also upgrade the binding posts to tube connectors.
A number of us have build threads in Danny's circle where we show how to do the different levels of upgrades.
Mike