New dehumidifiers, energy star, are very efficient. mine only heats the
basement a degree or 2 and only consumes 350 watts its 52 pint. An ac
unit may make your basement just plain cold. Actualy central air would
be as cheap to run as you window units and cool 3x better, more evenly.
Maybe minor duct upgrades could make central air workable. I had that
problem and just added one return. It was that or no AC