audio hu and sub questions

I got the 3000gt sl back in winter and i am still trying to get this stereo straightened out. First question:
I got a 2 channel amp and bridged it to make 500 rms at 4 ohms. i bought a dvc 4 ohm sub not realizing it was 4 per coil. so then given the options of 2 ohms or 8 i wired it in series for 8 ohms figuring i wont blow the amp. isn't there a better way to do that? 2 ohms plus a resistor in series or one coil per channel unbridged? i know a little about wiring but not enough. running the amp at 2 ohms is bad for it, what about 8? does that waste power or just mean its quieter at the same volume. please, any advice or insight would be appreciated greatly.

not as important questions:
alpine cda 9830 head unit can adjust frequencies for bands 1 through 4. each band is broken into 3 different frequencies. for example band 1: 40, 60, 90 hz. i can give band 1 up to +12 to boost the bass but idk how to only boost 60 and not 40 or 90. i would assume u can on an alpine but i've tried every button i can think of but to no effect. i don't expect someone to own the same hu so im just kinda throwing this question in for the hell of it. also whats band width? band 1 has 1.0, 2.0 or 3.0 and they're adjustable?? anyone know what that means?
lastly, for time correction measurements should i measure straight from the sub to my head or should i include the sound's path of bouncing off the inside of the hatch?

with regards to the amp, what type of amp is it? does the amp run each channel at 4 ohms by itself? if so, then just wire 1 channel to 1 voice coil and the other channel to the other voice coil, and then they are both running @ 4 ohms. need more info on the amp though.

The amp is a 2 channel by 4 ohm 200W rms and the sub is a 400W rms 4 ohm dvc. when i bridge the amp i get 500W and hook the sub in series with 8 ohms so i get more watts and don't blow the sub (not that i crank the volume anyway) but yeah one channel per coil would work. then i'd get 200W at 4 ohms. would that be louder or better sounding or put less strain on the equipement? whats better for it anyway more volts in the amp or more in the sub?

ok first of all, if the amp is 2 x 200 @ 4 ohms then this will be perfect. just wire 1 channel to each coil, and you will have 200 watts to each sub (total = 400 watts)

when you wire something in series, it cuts the power in 1/2 coming to the sub. so that amp pushing 500W and you running the subs @ 8 ohms will give the sub 250 watts (btw running something in a higher ohm setting will never hurt your equipment, just give you less power)

so 1 channel to each coil will give you 400 watts total power, doing what you are doing now is giving the sub 250 watts, so you will be better off doing it the way i explained.

Yeah that makes perfect sense, thanks a lot. my only question with that is what wire to use. i have some leftover speaker wire than came with the alpine speakers but idk if thats thick enough.

For that power any wire will work really... but you can get some thicker gauge wire from wal-mart... in the auto section...

with 400 watts 8 gauge would probably work just fine. you don't need anything thicker unless you are going with more power.