Power Kite has 18 built in collapsing and automatically resizing module positions. For example, If you publish no modules in the left modules area, then the left module will collapse.

This goes for all module positions in Power Kite, the top and bottom advert areas will also divide the area equally depending on how many modules are published to those positions. You can also align the left and right module positions (inset and outset panels) in your template parameters, allowing for different layouts for your 5 defined themes.