What to do with old Thiel CS-2s

I should also mention that these did not have double sticky stuff on the grills when I bought them, but after the amp blowup, the Thiel restoration included the double sticky tape.. Alas this precluded taking the grilles off, so they weren't checked as they should have been. And then when I did try remove the grilles it ruined the grilles and the surface finish underneath... Thiel might make good speakers but this was an amateur solution.. If they had asked when they did the repair I would have told them not to use the tape - grilles had been fine without it from 1987-1994. Oh well

Trying to replace the drivers with randomly chosen same-sized drivers would produce horrible results. Speakers have many different operating parameters that must all be right to work correctly for a particular design. Your chances of buying even a close match without careful research are zero.

I think your best alternative to original replacements for the cone speakers is re-coning. Hopefully your tweeters are OK. If not, repair may be possible.

I've seen many pairs of CS 2's sans grill, all had the dual sided tape, including the pair I purchased new. Perhaps you had a very early pair? The grills could be removed, unfortunately doing so would remove paint from he baffle. Not really a problem as the grill on this particular model were designed to be part of the smooth detraction efforts, so it would be unwise to play them without the grills, and once the grills were replaced, one wouldn't see the paint damage.
The CS 2's has a very easy impedance load, rated at 6 Ohms nominal/ 5 Ohms minimal. Here's Stereophile's measurements demonstrating just how easy a load it was:
http://www.stereophile.com/content/thiel-cs2-loudspeaker-measurements
I've heard the CS 2's in many different set ups and with quite a few different amps in my own rooms. I ran them with B&K ST 140s for some time. I'm surprised you preferred the B&Ks to the Krell. That was one of my favorite amps with them. I ended up using ss c-j and enjoyed that combo for many years before moving up the Thiel line and changing amps with speakers.
I wouldn't recommend using random off the shelf drivers. I'd suggest find used parts on line or just ditching them and moving on.

Funny. Mine definitely didn't have it originally. And when it had been on for 15+ years it was a bear to remove and did damage. Oh well. Yes, not a problem unless one wanted to look at the drivers (not to play them, just to see the condition). The nominal load was indeed easy, but it fluctuated over the frequency range. At least mine did. More than many speakers I think. There was no question the B&K did better than the Krell at least for my pair. Go figure. The Krell was better with successor speakers, but not the CS-2s. At least to our ears - always sounded thin and underpowered relative to the B&K.

I agree with everyone - random off the shelf drivers seem like a bad idea. Probably will ditch or try this:

http://www.madisoundspeakerstore.com/retrofits

I guess I might just list them on craiglist and offer them as "yours if you come and haul them away". Would be a shame to just trash the cabinets. And oh, by the way, the tweeters are trashed too. I am pretty sure our movers crushed all the drivers. Not any other likely explanation. I just wish we had caught it at the time and I could have put in a claim. Part of the issue was I couldn't easily check them because the grilles were so hard to remove! Oh well.

Did you see the graph on the Stereophile link? That is one smooth, easy impedance load.