I always liked the Aiwa solenoid decks - reliable and worked smoothly. I had one myself.

I found this website indispensable for researching decks when choosing mine - www.vintagecassette.com/

Has to be a Nakamichi

At the time, Nak ruled - period!!! They weren't always reliable and the 700 and 1000 models were terrible for dry joints or noisy connector blocks inside. By now, parts will be wearing out and although the heads have a good life I recall, the motor bushings, belts and pressure rollers may be impossible to get. When running, my 700ZXE was a wonderful thing and although black, the 682ZX has to be my favourite of all as the money went inside where it matters...

Tandbergs were unreliable clanky things, Aiwa's were nice if you can find an unmolested one, Pioneers had good design but no two were set up the same (The CTF 2121 that had rave reviews was one particular sample taken round each reviewer and production ones weren't always the same - see, review deceit was rife even then)

The one thing to watch apart from reliability is the eq methods used. Naks were different to earlier machines which often tinkered with the individual machine eq for best measurements. tapes made on one machine would be different to others. Nak's form of eq was eventually adopted I believe and later, the Dolby S machines used a Nak ZX9? as their master reference and all machines thus equipped followed this eq standard.

I know I'mnot helping, but one thing pertinent to me is that my old Denon machine's eq plays back old tapes nicely, but recordings made on it always sounded muffled when played back on a Nakamichi standard machine.