I agree with you. I purchased a set of Whelen TIR3 LED lightheads (they are made for emergency vehicles) and installed them on either side of my license plate and wired them into the turn signals. They are extremely bright. When my friends are behind me I am almost blinding them.
As I said they are a warning light with different flash patterns and made for emergency vehicles (course in my job I install them all the time) but they have a steady burn pattern that you can set and then wire them in so they blink with the turn signals. If you get a set, make sure you specify whether you need the vertical or horizonal lighthead, as it does make a difference in the way the light pattern spreads.