There's a trick you can do to get more direct shot of highs out of the dash...
Take the grill off. Notice the grill slits are extremely thick and deep. This creates a channel the sound has to follow. If you grind down the back of the grill a little to change the channels to slits, it will let a lot more sound out (try listening without the grills on for an example. It won't be quite that strong modified since they will still block some.) Downside is if not careful, it can be an obvious change which might look a little odd. Also makes them slightly more vulnerable to a splash. I use a razor blade tool to clean them up after sanding or grinding. Don't go TOO far... Not all the way to the face.
It might get you the sound you're looking for, for free... Listen without your grills on to see if it's what you're looking for. If not, perhaps a brand of speaker change. Infinities are brighter than polks (which actually is why I don't like em, but if that's the sound you like, then you very well might. That's why speakers are so important for each person to choose themselves.)