A lot of brightness with LED haws has to do with placement in the casing. A lot of people will suggest Whelen Vertex. I personally recommend the Axixtech TRI's or SoundOff Universal Undercovers.
FYI to all those interested, there are 1000+ threads on LED haws which can be found by running a search...however you can also check out the "equipment reviews" sub forum which has comments about Sounds off, Whelen and Axixtech LED HAWs.