Im thinking about getting something liek sony xplodes to replace my stock speakers in the car. Will it sound better right off the bat, or will I need an amp? Stock things sound like crap

It would sound better, but I would definitely upgrade with an aftermarket amp. Under powering speakers will destroy them quicker than over powering them!

do you have the stock headunit or and aftermarket one? with MOST stock systems i would recommend changing the headunit out first and powering the stock speakers, as this tends to sound better than running new speakers off of a typically weak HU, however the stock systems in our cars suck SO much, that the only way to get good sound is to replace the headunit and speakers, or add an amp with the speakers. however, you will probably see an improvment in sound quality with the new speakers, so try that out first and see if you like it. if not, you can upgrade other things down the road.

if you have something other than the stock head unit, it should sound great. i had the sony xplods for a while, they were alright. they are a good speaker if you already have subs(tweeter is very loud, and very clear), but dont try to pull any bass out of them at all, its pathetic. it puts out an annoying popping sound because of the poly cone. you should try the rockford fanatics!!!