I've been in the business for some years now and over those years our
crew has learned the 3" by 21" Ryobi inline belt sander is probably
the most versatile.

It is as durable as any and being inline you can lay it on it's top
and use it upside down to sand smaller pieces of wood.

The last time I checked it cost around $150.

It is also sold as Craftsman as Ryobi manufacturers it for Sears.

As far as a palm sander (ie 1/4 sheet) goes I had the best luck with
the DeWalt.

Hope this helps.