What made you go with the infinity reference? I'm thinking about changing mine out as well. Did you use bass blockers with them? I've been researching and lots of people seem to be changing the dash speakers out. Sounds like it's worth it. Is it just a matter of getting crisper highs with the upgrade? Did you need to turn the treble down after changing out? Thanks!
I went with infinity only because I've had good experiences in the past. I'm not enough of an audiophile to compare kicker to Polk to infinity. Haha.
Changing out the dash was worth it as I think that's one key place - because of the way the system is balanced - that the weaknesses of the stock speakers show. Most of the sound you hear when driving is r dash speakers bouncing off the windshield so improving those is an easily noticeable gain.
I did not use any bass blockers as I think the AMP is already tuning for certain frequencies, if it's not, then I have not noticed a negative side-effect of not using them. Most noticeable with dash speaker replacement is probably brightness and clarity.. for me anyway... a high-hat cymbal sounds like one, the sound from the dash has good defenition now, crisper and more clear than with OEM. It's a 10min job to replace if you have the ratcheting torx tool (several inexpensive options mentioned earlier in this thread)
I've made some adjustment to the basic equalizer, but I do that often anyway as I listen to a lot of different types of music so adjustment was always something I did.