[Hyper4mance2k]

I found that replaceing the stock 3.5" with a decent coaxial speaker made a world of difference. The stock 3.5 seems a bit muffled and the stock tweeter is only .5". Replaceing the stock mid with an upgraded coaxial adresses both of these problems.
All the speakers in the car are wired at a 2 ohm load. The rears are 2 ohm, the front door speakers are 2 ohm, and the dash mid & tweeter are 4 ohms each wired in parallel for a 2 ohm load. I simply replaced the stock 3.5 with a good old 4" Kicker I had laying around, and it made a world of difference. The sound was much fuller and brighter. Fitting a 4" speaker took some massaging, but if I were to do it again I would just replace it with a better 3.5" coaxial. YMMV.