Upgrading base stereo, any input on this setup?

ChipsWithDips

OK I'm starting to concede that I probably should get an amp. I just noticed these speakers are rated 2.7Ohms, and the headunit is only good down to 4Ohms.

Considering this one at the moment, unless anyone has a better recommendation.
Amazon.com: Amplifier - Model#: P9004: Car Electronics

It has 4ch but I would only be using two. Although with the filters on it it looks like I could actually ditch the passive crossover and make use of all 4ch, would that be worth doing?

Or should I just go with some other speakers that are actually 4ohm (like the DBs) and just don't turn them up very loud, and no amp?

Agh, making decisions like this kills me.

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