[bmwm3guy]

1- Bass Blockers, or better know as crossovers, channel the frequencies of audio going through the wires, therefore you can channel the bass to your subs, mid to your mids, and high freq. to your tweeters.

2- Unless you have high performance speakers, the stock wiring should be fine unless you can here distortion, but that would most likely be the speakers before the wiring.

3-Junk, you will never replace 10-12" subs with 4" ones. They may be good bass, but nothing compared to 10s, 12s, 15s, or 18s.

4-Most of the time amps require good air circulation because the transformation of power emits TONS of heat. If you have a 800Watt amp running at 50 watts of power you wil have no problem, but otherwiose ensure the amp gets enough air so that is does not ofver heat. Under the seats of your cherokee shoudl be fine, but I dont know te clearance the amp gets so it really depends. Try installing a small fan or re-direct an air vent.

Hope that made sense.