I have Kenwood 4"s in my dash. They will fit, you just have to take a little time and make some mods. The speaker magnet was too deep and it was hitting the vent. If you have a heat gun, then you can just heat up the vents and they should mould easily so that the speaker will fit in. Also, you may need to make some adjustments to the mounting lip of the speaker itself and you wont be able to secure it with all four bolts. I just used three. But yes, 4"s will work and they will give much better sound than the stock 3.5"'s. The door speakers in my case were were 6.5"s. This is just a direct fit. And, mine being a coupe, the rear speakers were 6x8", but you can easily buy an adapter for about $10 so that 6x9"s will fit. This will also give you a little better sound. I'm not postive on the coupes, but I'd imagine the front four are the same, and to my best knowledge, the rear speakers are 5x7"s. Hope some of this helps to answer your question.