1-this could be a few things... one of which is merely be the alternating current +/-... because they are so efficient, my cornwalls also did the same thing until I added a filtered power source and I can replicate the buzzing by plugging my amp directly into the wall outlet. Now that I use a filtered power, I have an extremely black floor in my system with superb separation and spacial qualities.
2-as others have stated, crites is an OEM type cross over replacement... so if that is what you are looking for, go that way(they are also more reasonably priced). if you want to upgrade your cross over components, an ALK designed unit is a really good way to go... as are the cross overs that aletheia audio builds.
3-crites CT-125's are a fairly inexpensive replacement for the Klipsch tweeter if you feel the need.
as far as the cornwall and solid state goes... don't let anyone tell you it's not a good match up. it's simply not true, it's just different... and in some cases, not that much different.