It is possible. As the Ampeg 810''-cabs have 4 Ohm, you are always allowed to hook up cabs with that load. So if you have two 610''-cabs with 4 Ohm both, why not using them?
If you have elder 610''-cabs with an impedance of 5,3 Ohm there will be no problem at all, because you are always allowed to use higher loads on transistor poweramps.
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