Here is a good start for you: http://www.hifipage.com/loudspeaker-specifications-explained-11/
There are 2 main opinions on buying audio equipment on a budget.
1. Buy the best speakers you can afford and fill in with the receiver and amps.
2. Buy the best receiver and amps, then use the leftover and buy the speakers.
I go with number one myself. Crappy speakers will make the best equipment sound like ****.
The best way to buy speakers is to listen to some. What sounds great to someone else might sound like crap to you. If you can't find anyone with aftermarket speakers, go to a car audio shop and listen. Yeah, they will push their brands but going to 2 or 3 will give you enough information to make a decision.
Do get some kind of sound deadning material to control vibration.
Good luck and post up what you get
2014 GHIG GT Premium - Track Pack, Comfort Pack, Rear Camera, GT500 mufflers, Boss 302 Grille with stock fogs.