hey guys i heard that when running a sub off of an amp...its best to get a head unit that has sub...not just rear...but sub output rca's. meaning using a deck that has 3 sets of pre-amps, front, rear and sub
i have a friend that said he has all three and there was a huge difference in sound quality running the sub pre-outs over the rear pre-outs
It's probably because hooked into the rear rca's the subs are now affected by all of your EQ settings and not just the settings on your amp. With the dedicated sub rca the sub should only get EQ signals from the amp so that you can adjust your woofer separately from your speakers, also the sub rca will give you a dedicated sub woofer volume control unlike the rear rca. Using the sub rca is a much safer way in my opinion but, if your okay with your woofers being set at the same levels as your speakers then go for it.