I personally have a CED7000 that works really well ($120). Its small and is easy to use with many features and a decent size memory for multiple strings. You can also by the RF version ($160) that can wireless link to a separate CED BigBoard display ($180) up to 50 yards away. The only downside to this model is that is has an internal re-chargeable battery.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." B.Franklin,1759