I use a 48cc brushcutter most days. It's a Kawasaki. I would highly recommend Kawasaki. I prefer them to Stihl, and they are less money new. Still a lot of money for infrequent use though.
Keep a lookout on Ebay, always seem to be Stihls on there, among other stuff.
Maybe stick a wanted add on gumtree, or have a word with a mower repair shop. There are loads of brushcutters hanging around in garden sheds, some quite good ones, that are never used. Trouble is, finding them.
I've used the cheaper end of the market. I once had a Sanli, it paid for it self, so it wasn't so bad. Not quality though. Parts are not cheap for them either. Unless you really are just twinkling around the edge of the lawn every week, i'd be inclined to leave them alone.