I am a high school student too. I paid for every thing in my system by my self. Don't bother trying to squeeze an 8 inch in there. It's not worth it. My system is as follows: Pioneer 4100 CD ($300 installed), Infinity components ($100), Pioneer 2-way 6x8's ($55), 2 10" RF with box and RF 150a2 amp (bought used from a friend for $350), amp hook up kit (%45). I installed this all my self except for the headunit cause it was free. To save around $200 don't buy a changer. At least right now. Best Buy will install headunits over $99 for free if you buy it there. But buy your speakers online. At least 1 pair from crutchfield cause they will send you everything you would ever need to know about installing your system in your Explorer. If you definately need the thunderform (which i think is a good deal I plan on getting one some time) you are at $400-$450 already. Then a headunit $250-$300. Speakers $175 for all 4. That's about $800. Then if you can't install it your self that's a whole lot more. Don't just buy the thunderform though. You will be sorry. The amplified thunderform is 100 watts. Match that up to your stock speakers and you won't hear anything but bass. I would say save up for a little while or do what I did. Buy a headunit now. Save up for 2 months buy speakers. Then buy the sub. One question. Do you have a job? If not get one and put your checks in the bank.