There's a Denon DRS 810 with lots of miles left on it, wrapped in plastic and sitting on the corner of my workbench. Used to use it to make tapes for a 1992 Saab which was finally traded away. Given the format, it's about as good a recorder as I suspect you'll come accross. Make me an offer.

Look to Musiciansfriend for some Tascam models, Teac's pro group. Most are pretty well made. Like you, I have many cassette and will probably buy one more cassette deck within the year. I had 2 Nakamichi's that developed motor problems and I have an NAD that is still running. I don't listen often, but it is tons of free software waiting to be played. If you buy cheap poor tape speed will be an issue. I think Sony and Denon's higher end models would work well.

You shouldn't have any problem finding quite a few used decks on ebay or audiogon. I picked up a near new NAD deck last year for 20 bucks.

Those things are dirt cheap now.