in my opinion spend for as good of a front componet speaker system as you can afford and the rear speakers are not important. If you insist on rear speakers than get something decent but in most cases, especially call cars like a Corvette rear speakers aren't needed.
As for speaker brand and model selection the only way to choose is to go around to a number of car audio shops (specialty shops - not big box stores like Circut city, Best Buy, etc) and listen to various sets and see what you like the sound of. YOU are the one that has to listemn to the speakers so you need to know what you like the sound of.
When listening to speakers listen to them thru the same model amp you are buying if possible or at the very least the same power level per channel of amp. This means if you are buying a 50 watt/channel amp (as an example) don't listen to the speakers thru a 25 wpc amp or a 75wpc amp.
Take in your own prerecorded CD discs to listen to that you know very well and listen carefully to the differences between the speakers. When you hear a set you like you will know it. Many will sound very, very similar than all of a sudden you will hear one that just pops at you and says they are the ones you have to have.
here is a good page to read for basic tips of how to listen to speakers to evaluate them:
http://mobile.jlaudio.com/products_c...php?page_id=96
Theoretically all speakers should sound the same as the only job a speaker has is to accuratlly reproduce the music as transparently as possible without introducing any coloration of it's own but realistically that never happens and pretty much every speaker you hear has it's own particualar "sound" to it. Some are better in the highs, some have more accurate midrange, etc. Some sets have better passive crossovers than other sets, etc and all of this is important to the overall sound and quality of the speaker. Because of this you have to listen to them yourself and see what YOU like the sound of.
27 people on here can all tell you that "XYZ" is the best speaker on the market but you very well may listen to it and hate the sound of it but prefer the sound of speaker "DEF" instead. It's all very subjective.
Also, component speaker sets come with a basic passive crossover network to divide the frequencies between the midrange and tweeters but some brands also offer an upgraded, better quality crossover network that you can purchase seperately. If you are going with a very high-end speaker system you may want to look those upgraded crossovers if they are avaialble for the speakers you decide on as they can make a big difference in sound also quality also.