new speakers dont always need an amp. if you get coaxials, you CAN power them just off the HU, but most people amp them just to make them sound better and get louder/clearer, but you dont have to. if you get component speakers they should be amped.
component speakers are alittle more pricey than coaxials. component speakers use separate woofers, tweeters, and have a crossover that comes with the speakers. this sends out the low frequencies to the woofers and the high frequencies to the tweeters, giving them great clarity.
coaxials usually consist of a midrange or woofer with a tweeter over the cone, and dont sound as clear/good as components, and they dont have crossovers with them
oh and i dont mind answering any questions...glad to help man