Steve,
Mike is right. The A820 would always be the right choice, because it is pretty much the absolute mechanical reference in analog tape recorders. It doesn't come cheap, though.
The A810 also winds a very neat pack using the lower of the four spooling speeds. But if you use a lot of acetate tapes, I indeed wouldn't recommend the A810. A better choice would be the B67 in that case, which does have controlled tape tension during breaking. Not as good as the A820 obviously.
An A80 is always a very good choice as well. Not as cool as the A820, but more friendly to your wallet.
In all cases the main question will be whether you have the possibilities to restore/maintain the machines yourself. If not, you need to get it from a proven source, because any of these machines you buy cheap on ebay will have some issues, big or small.