In my teens I was a Fostex X-15 user, and only got rid of it when it decided to give up on me. Years later when I was slowly getting myself back into making music I decided that I needed another 4-track.
Since my days of the X-15 a lot had changed, and I stumbled upon the Tascam PS5. It was just what I was after, a 4-track but much much more. The PS5 also had an on board GM module that you could use for drums and bass and rhythm. It was fantastic, and no bigger than a video cassette.
I bought my PS5 off eBay, and sold it there too. One thing that really sold me on it was this article from Sound on Sound. It is really detailed and tells you all you need to know.
I know that by today’s standards the PS5 is huge. I think you could probably get four Boss Micro-BRs into its casing, but it was a real find back then in 2002 and still a worthwhile machine today.