I started with a pv10a which seemed glorious as long as I didn't push too hard. After leaving c-j for a number of other brands, I eventually came back as follows:
Pr 17 nice
Pr 17s2 big improvement and easily the best buy
Pr 16 nice, but not really an improvement over the 17s2 to me
Pr 16s2. again, nice but for $$ the 17s2 was a better buy
CT-5 big step up in transparancy but still tonally wonderful. My favorite preamp that I have heard.
I have not heard the current line up of ET-3, ET-5 or GAT. My only temptation would be to consider an ET-3SE with phono and down size the CT-5 and pr 15 to save some money/space, but only a thought at this time.
I also have not heard the CT-6 or the Pr 14 and 18's, but I assume they all have similar sonic signatures. I personally prefer the c-j sound to any solid state I have heard or to the Audio Research pieces I have tried. Of course, everyone's taste is different.
Regards,
Paul