When you combine a high output amp with a lot of gain, to an efficient speaker - you get noise. The diaphragms are probably fine. Damaged drivers either don't work or sound so bad you can't stand to listen to them.
The stock C II crossover is awful. It needs to be addressed, but I agree with Shakey, so does that amp - it's just not a very good sonic match with horns.
Think of a crossover the same way you think of tone controls. The different type slopes control the total amount of energy seen by each driver, and changing those slopes (and alignment type) has profound effects on the sonic signature of the loudspeaker.
If you were to compare a Klipsch rebuild by Michael Crites (sorry Bob, but I think it's time everyone knows you're pretty much down to drinking coffee, taking calls, and giving that Hemi a daily workout) to one of Al's simpler designs, you would notice the following:
The Klipsch rebuild would allow the speaker to open up very fast, it would sound very crisp, and the midrange horn would dominate the sonic signature. That is, a very strong midrange presence with some bite. With your Adcom, it will come off a little harsh, and if you listen loud, listener fatigue will settle in pretty quick.
Al's "CornScala-wall" by comparison, wouldn't seem quite as efficient (you would need a wee bit more on the volume control to get the same effect), the loudspeaker overall would sound a little more laid back and smoother, and the midrange would sound more balanced in relationship to the other drivers. His crossover also allows you to adjust the midrange to suit your personal taste.
So how to choose? They are priced about the same I think. You are choosing between a fast, punchy and very dynamic sound and something that's very open, more relaxed sounding, and velvety smooth.
I think you should do both. Recap your originals, which is not much money at all, and buy Al's later.
Start saving for a low powered tubed integrated amplifier. Seriously, you don't need a 200 wpc noisemaker. My last 555 was almost 10 years ago, and even after I changed out the big electrolytics in the power supply and a couple of other the things, my little Scott 299B with 22 wpc ran circles around it.
If you change out the horn, which is definitely a good thing, I'm not sure that you will be able to use the stock network without some modification (I don't know if the horn requires additional attenuation).