How are these speakers different in sound quality?
I've used infinity with my old car but I have no idea of how polk audio is different from infinity.
Anyone knows?

 

infinity tweeters are too harsh, and polk mids lack midbass imo

 

the best thing you can do is A/B them. Go to a shop and listen to them.

 

I've used both... like both... to me depends on what I feel has the best sound at the time of purchase.

You can't go wrong with either one. Just listen to them and see which one you prefer.

 

focal ftw

 

I think the infinity tweeter's are pretty harsh as well (I still have 62.9i in my civic). However, I really liked the mid bass in my Polk MMC 650 (component set) when I had my S2K. I do like Polk's home theater speaker's as well.

 

Unless you're buying higher end speakers you honestly shouldn't bother replacing them. I hooked up a HD600 Amp to my hi's with stock speakers and they're keeping up with my 10W7's in the trunk.

Personally tho. I like infinity and JL. JL ZR's are amazing.

 

Yeah, I've been thinking to upgrade my speakers but decided stick with stock speakers until I put some mileage on my car.
But what I wanted was not loud volume but rather better sound quality. With stock sound system I don't even go over 20 in terms of volume. (Looks like 10-11 is most comfortable to me) That's why I thought I don't need aftermarket amp but probably new speakers would do what I want. Still not worth?

 

you need power to make sound quality as well as good speakers. Power makes the speakers not have to work as hard.

 

I actually like the way vocals sound on the Infinities. As everyone said, tweets are harsh. Midbass was decent. They work good with the stock amp. I really enjoyed mine but the time came when the two 12W6s just overpowered them. If you plan on really cranking them with an aftermarket amp, there is much better out there.

 

When I compared Polk to Infinity speakers, I noticed that Polk sounded better at stock amplification. Infinity ONLY sounded better if there was added amplification/power. That is a generalization, you'll need to go do comparison shopping... but when you do... have them disable/enable extra amplification to do the extra comparisons.