We did this last year. The unit on the right is a self contained unit, just hook up power/thermostat and duct work and everything is ready to go. The crawl space under the house is very small.
The unit on the left is a split system and the air handler and evaporator(cold part) is in the attic. The line set going up to the attic has since been wrapped in white metal, so it doesn't look to bad.
Both of these are 2.5 ton heat pumps with electric backup.