recommendations for new air conditioning units

[Bruce Ellerd]

I need to buy new air conditioning units for my four-plex. What is recommended for the best product to cool the unit well, but not buy a unit that cools a 2,000 square foot house.

What I have is four 1 bedroom, 1 bath units that are 531 square feet. The current air conditioning units are side feed and fairly small, about 28" square. 

I've seen units for sale at Home Depot for about $350 that are rated to cool an 1,100 square feet house and feel it's a waste to buy an a/c unit that will cool double the square footage needed.

Any thoughts from the experienced?

Thank you,

-Bruce