Regarding buying in America, beware of import duties!
I bought a gps recently on the net from a US online shop, which on the face of it was a lot cheaper. By the time the stinking dept of Customs and Excise had taken their cut I may as well have bought it in the UK.
Regarding which headset to buy, I decided to opt for a basic Seinheiser as everyone seems to have a Dave Clarke. Its pretty comfortable and I reckon a bit more solidly built than a DC. Price wise they're about the same.