I have owned two pairs of TC-50's, I slightly modded one pair with cardas wiring, Edison price jacks. Sound became a little smoother, but not by much. You can remove the felt from the front baffle which will dramatically alter the sound, you have to choose which way you like it in combination with rooms, equipt. etc. biggest improvement was to switch speaker cables to cardas golden 5 hexlink. Last year I had to replace one tweeter, one went bad, you can get exact replacements from Madison Sound, it is on the web. Audax replacement tweeters were $25 or so each, pretty cheap. The new tweeters took a few weeks to burn in and loose the racy treble.
I have never heard the TC-60s but I believe they are not a true John Bau design, Spica was bought by another company. I have heard from one dealer that the TC-60 was not as good in some ways as the TC-50. The TC-60 is ported, uses different drivers, I think a metal tweeter, probably can handle higher power, probably a little more efficient, may be slightly deeper in bass(?)
I have never heard the TC-60s but I believe they are not a true John Bau design, Spica was bought by another company. I have heard from one dealer that the TC-60 was not as good in some ways as the TC-50. The TC-60 is ported, uses different drivers, I think a metal tweeter, probably can handle higher power, probably a little more efficient, may be slightly deeper in bass(?)