I currently have around 8 cassette decks I'm about to list.
Of the Yamahas, find one with Play Trim. It works very well and you can get a lovely sound by "tuning" it.
I have 2 with play trim, including the lively 580SE.
I may moved into 3 head decks as I wanted to tweak the recording as they happened (2 x Technics and 1 x Aiwa).
I also had a 3 head nakamichi 300E. It sounded stunning, but the aiwa was close behind.
All decks will need belts at this age. I found Technics the most reliable, and ones with dbx noise reduction sound very hiss free.
OP, you don't mention what price you have been offered for the Yamahas but you can get a decent deck for £40. I sold my Nakamichi for £300 last year, to give you an idea.
I'll list my current ones on here very shortly but it'll be best to buy locally, preferably demo'd.
Also, try and find some nice TDK SA tapes to get the most out of recordings.