Is there an Echo in here?
I fourth an Echo. I have one I bought 9 years ago, the GT-230. It has the "bump head" spring loaded spool. It is a great trimmer that has not let me down, ever. To go with that, the Echo Crossfire trimmer string/line they sell is good stuff too. My dad had an older Echo GT-2000 that he bought back around '97, and it's still doing well.
Nearly everything for yardwork I own, except for the lawnmower (Toro), is an Echo. I have the weed eater, the ES-250 leaf blower/vacuum, and the CS-400 chainsaw. Great quality. From what I know of Echo equipment, they are considered "prosumer", meaning the build quality of professional equipment, but marketed more towards residential consumers. Can't go wrong with an Echo, especially with the 5 year warranty on the new equipment.
Thicker line may help your weed eater, but be very careful doing that. My father in law used .155 size line on his weed eater that was designed for .105 max. Not only was the engine overloaded trying to swing the heavier line around, but he also broke the cable shaft, twice. He has since went back to the proper size line after repairs.