Having an RCA signal will have a higher line voltage output, so you'll have a cleaner signal and can turn down the gains a little, cleaning up the noise as well. Plus a dedicated subwoofer-out from the deck will mean you can turn it off, adjust the frequency and level on the fly without it affecting the stock speakers. The only downside if using converters is that if you crank the bass on the deck, you increase the chance of distortion from the stock little speakers, but you won't notice it since it's downed out from the subwoofer. For the sake of testing, crank the bass on your current setup, turn it up to a good level that isn't quite distoring, then unplug your sub...I'll bet your stock speakers will sound like crap from working harder than they were designed to for those frequencies, but you never noticed it.

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