ok here's my situation, I had to replace one set of my infinity 4x6 plates. One of the cone's cracked and was making noise after being pounded full range everyday in my rear deck for three years ... anyways I bought some polk audio 4x6's to replace them. Now I am thinking about getting another set of the polks for the doors so i will have two matched sets. I've heard it creates some kind of canceling effect when you have two sets of the same speakers. or is this only true for subs? I tried using the polks and infinity's together and I just can't seem to get things they way i had them mostly because the polks don't need half as much power as the infinity's so it sounds off at various volume levels. what do you all think about polk products in general...i was impressed by the two way crossover's in the polks.. the infinty's only have one way protection for the tweeter...anyways I wanna go tonight and get them so if you have any advice for me it's going to have to be in the next hour or so thanks. peace