Originally Posted by VA561
It doesn't matter if it is solid state or vacuum tube but would prefer mid to late 60s if possible. Seventies if no later than 73.
You'd be slightly better off going a little later into the 70's. The reliability was really improving, plus the chances of getting a low-hours set is better, as many later 70's models were bought as an extra set instead of the primary set.
Then again, it depends on how much you're going to use it. Mainly my opinion, but I'm sure others will agree.