i'd recommend an wilson or an babolat racket.
wilson has not that big amount of different rackets (as head for example has), but the ones they build are great.
if i hadn't a wilson racket, i'd choose a babolat racket. nice handling, good for top-spin players etc.
i'm just talking about the "tour-level" rackets here, i don't know the others =)
but as always - test some rackets before buying. if u made a desicion, try out some strings on the new racket. and then start playing, and, hopefully, winning