even for budget reasons, I probably wouldn't go with emersons. They'll probably blow just as much as factory speakers.
These lanzar speakers are really good sounding and won't break the bank:
http://www.onlinecarstereo.com/CarAu...e&SortOrder=0&
You could also go for these hifonics 6x9's, but it would be recommended to power them with an amp:
http://www.onlinecarstereo.com/CarAu...s_ZXi_693.aspx
it's better to put components in the front and 2 way coaxials in the back. Most of the music will be coming from the front and you should probably power them with a 2 channel amp....have your head unit power the rears. Usually rear speakers are just for fill, but if you have passengers in the back, then you should get a 4 channel amp.