Since you have the batteries, I would go with two banks of 400 amp-hours each. Install the banks opposite each other to help with weight distribution.
Two banks will simplify doing equalization charging. Be sure to wire each bank in a balanced manner.
If I were starting over, I'd jump right to a 48 volt bank--but that may not work with the existing solar panel array. For panels in series it is needful to have the amperage the same on each and every panel.
I'm glad your Aims is hanging in there and meeting your needs.