I use a snapon DA for rough sanding and getting a car stripped down in a hurry. Great unit.. not super heavy and has good motion rather than a "side/side" like alot of cheap DA's have A good solid motor that provides uniform movement always and doesn't have your compressor cycling 100x an hour! $120
http://buy1.snapon.com/catalog/item....re&dir=catalog
I use a cornwell random orbital finish sander for well.. my finish work. For getting that final work done and getting everything perfect. High RPM w/ high grit sandpaper produces a great finished surface to paint. $180
snap on offers a similar unit
http://buy1.snapon.com/catalog/item....re&dir=catalog
Buy good tools... they last longer, do a better job and won't leave you hanging on a sunday night at 9pm when harbor freight, etc are close and your trying to get a job done. You spend more on it.. but its worth it!
DIY guys craftsman usually works fine.. if possible buy up older craftsman tools at garage sales, etc.. they are much better build quality than the stuff out there today. Plus the lifetime warranty still applies to most of the hand tools.