I highly recommend Focal speakers, but no matter what speaker you choose you need an amp. More then likely the speakers you choose will be 4 ohm and the stock radio is 2 ohm also your radio doesn't put enough wattage out to drive new speakers, you can damage speakers by underpowering them.
Listen to Bryan he knows what he's talking about. There are several older threads on here in the sound system section. Go check them out and then consider a budget and you get more for your money.
Install Amp and speakers at the same time. Wait if you have to ($$$). I went mid-range with J&M, Focal is another really good brand, Many have indicated to stay away from Boom ll, Boom lll but my advice to you is to listen to other systems and then decide for yourself.
This x2 You can get a higher quality speaker, but you are not going to really notice it going anywhere besides the parking lot. I have ran 2 different sets of Focals now and have been overall happy. Check out Soundzcustoms, they just added another lower tier kit.