sub output vs regular output

I have 2 options to wire rcas to my amplifiers. 1: run f&r rcas from the head unit to the 4 channel amp, then use the amps non fading preamp outputs for the sub amp. 2: run f&r rcas from the head unit to the 4 channel amp, and run rcas from the sub output of the head unit to the sub amp. I thought the sub output from the head unit is just a volume control to be adjusted by the head unit. I dont want to control it, I want it full blast all the time. Would there be any differences or advantages between the two methods of wiring? I am planning on #1. Thanks!

Ok I gave too much info. Should the sub amp be hooked up to the head units subwoofer output, or the amplifiers non fading output? I will never need to adjust the sub level.

If the deck has a sub output why not use it...just set it and don't ever touch it...same as never needing to adjust the sub level

yeah, do you ever plan on having a girl in the car with you?   If not then do it your way. If so, they tend to like a "tid" cough less bass then "all the way up".99 Blazer LT.   Yellow Top. Big 3. Infinity Kappa Speakers All Around. Jensen CD/DVD flip out. 2 Infinity Kappa Perfect 12DVQs powered by a Alpine PDX600.1 (in one custom box, building a FG box)

[QUOTE=kirktcashalini] yeah, do you ever plan on having a girl in the car with you?   QUOTE] My wife - I have a cut off switch for the sub amp but I turn it on when she just keeps blah-blah-blahing So you guys are saying that using the sub out off of the deck is the more popular way to do it?

of course! Using the subwoofer out will actually give you control of the subwoofer! Now you can get rid of that switch! what kinda HU is it?

Ok, I didnt know you did a cut off switch, thats a good idea, I have contemplated doing one on mine as well, but I have an easy knob to turn it down easy. 99 Blazer LT.   Yellow Top. Big 3. Infinity Kappa Speakers All Around. Jensen CD/DVD flip out. 2 Infinity Kappa Perfect 12DVQs powered by a Alpine PDX600.1 (in one custom box, building a FG box)