Also the reason Im confused is because at best buy they tell me one thing, and a custom audio shop is telling me that wiring is completely wrong, and that theres a plug that supposedly came with my mono amp that will allow me to run speakers off it.. but when I went back to best buy they said thats impossible and they are crazy.. this is so ridiculous.. I want to learn everything the right way so I can just do it myself Im so tired of all these conflicting opinions..

the plug allows you to use an input from your speakers. but they likely used rca cables from your HU. thats the proper way to do it because you can adjust it separately.
mono amps have one output. yours is rated "300 watts RMS x 1 at 4 ohms (500 watts RMS x 1 at 2 ohms)" you have 2 4ohm subs wired in parallel (like bb did) equals 2 ohms. so the short story is bb did it right to feed your subs the most power from your amp (250w rms each)

ok that makes more sense, so when I get my new kenwood 1800w i should wire it the same way then?

yes, you will likely have to upgrade your input power wire depending on what they ran, adding a cap, possibly doing some ugrades to your car electrical system. your alt probably wont like to give that much for too long.

thanks for the advice i really appreciate it