Dash speakers from amp or HU?

I am getting ready to put new speakers and amps in my truck (2001 Blazer) and I'm trying to decide how to run my dash speakers. My truck has 6.5s in the front and rear doors, and a pair of 4x6s in the dash. I've got a 4 channel amp to run the two pairs of 6.5s, but I am debating whether to invest in a two channel amp for these dash speakers or just run them from my head unit. HU is Alpine CDA9831 and dash speakers are Polk Momo MMC460s. Any thoughts?

I appreciate the help!

IMO, I would run them off your HU, or do away with them completely, you have 6.5's in the front and rear doors, you can focus on those and give you sufficient mid and high range.

But if you absolutely want them, the HU should power them enough as to where they won't be too bright, just as moreless a fill.

I agree, even brand new, the 4x6's will not give you sound quality your looking for.  Another way to go would be to run components in the front and place the tweeters in the 4x6 locations.  

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