I own a Premier 16 Series 2 that I am very happy with. Have not heard the ET3SE so I can't offer any advice regarding which may be your better option. Regarding age issues, the CJ units in general are very well built and typically use very good parts. I own two of their amps and two of their preamps, the newest being more than 10 years old, and have never had a problem with any of them.
Regarding the sweet spot for their "older" preamps, my vote goes to the 16. Price wise you should be able to pick one up for not too much more than $3k.
Regarding the sweet spot for their "older" preamps, my vote goes to the 16. Price wise you should be able to pick one up for not too much more than $3k.