both require basically the same steps. Either way you need to take the signal from the headunit (via LOC if your on stock HU) to the amps. Then, you need power, remote, and grounds for the amp. Then you run speaker wire to either your subs or back up to the headunit where you can connect in to the speaker wires.
As mentioned, you NEED to amp the subs; the headunit can provide enough to power to produce a reasonable sound from your speakers, but not subs. This isn't to say you wont want an amp for your speakers- especially if they can handle more than 20 watts.
Post up brand and models and any info you've got about your speakers, subs, and amp.
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