External microphone recommendations for camcorder

[Moontrash]

I've noticed that camcorder microphones deliver fairly good sound as the models get pricier ($800 - $1000). Strange thing though, it seems if the higher priced model prosumer microphones are all internal...and obviously small. Why is it when I look for a external mic that most are the fairly large size boom mics? Also, a lot I see aren't 5.1 audio...just stereo etc. Can ya'll recommend an external mic for a prosumer camcorder that isn't bigger than the camcorder...or very pricey?

[smrpix]

Rode and Sennheiser make quality products. See if there's anything in their lineups that suit your needs.