put i think 2.5s in the vents and it sounds GREAT, for the cheap ass speakers they sound just as good or better than other home made McGuyver jobs i've seen in other z's doors @ kick panels + you can take them out at anytime w/o cutting into your panels or dash, my heater hasn't melted them when I turn it on it just blows hella hard out of the defrost vents. Warms the car up just as quick as before. These combined with the stock 4's by the ears and something decent in the back will give you a real...nice surround sound setup. Do it. Well worth it.