in my opinion the best speakers are focal. they have several lines all varying in price range but are very $$$$. mb quart are also excellent. they come in the discus, reference, premium, and q series. stay away from their entry level (discus series) because their not very good. otherwise my advice to you is to go to a local car audio shop and listen to as many brands of speakers and choose the brand that sounds best to YOUR ears. everyone has different taste so don't listen to the salesman because he's just going to try and make a sale.
here's my top 5 list of speakers from best:
1)focal, 2)mb quart, 3)boston acoustics, 4)infinity, 5)alpine.
btw here's my set up

alpine CDA 9813 head unit
alpine CHA-S634 6-disc changer
mb quart q series 5.25" components for the front and rear
alpine mrv-f540 amp
rockford fosgate HE2 12" subwoofer with q-logic box
rockford fosgate 401s amp