If you run them active, start with your tuning really high (around 3.5 - 4Khz) and move down from there. That way you don't burn them out. It takes about 1/4 of the power for your tweets compared to your mid-range or lower. Chances are your ears will bleed before your tweets do. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
You can either use an active head unit or an amp that is active capable. Tuning at the head unit is usually "better" but having a amp that is active capable can sometimes be cheaper if you already have a HU you want to use.