To start very easy only, go to the IASCA forum to get a general knowledge of ICE setup. Get to know what is SPL and what is SQ, and proceed with the choice you wanna.
SQ and SPL will be totally different setup, so make sure you get the correct equipment for the setup.
Once confirmed what setup you looking for, then only go window shopping....dun just go and purchase this and that. Basically you need one head unit, one front component set 6.5"inch, one sub and two amp.
Then make sure the amp meet the requirement of the speaker, not speaker meet the requirement of the amp. So choosing speaker first would be the right choice, but go for bigger watts, rms not PMPO rms.
Oh...go to IASCA plenty to read there....cheers!!