Here's the HS3000, for those that want to compare/contrast, to make the best choice for yourself.
Samsung HS3000 Stereo Bluetooth Headset :: MobileFun.com
I've been swearing by these bluetooth dongles for a long time. I spent a lot of time searching for the right one (starting w/ the cheap ebay ones, then finding other home versions, then eventually finding the HS3000 for the right price).
Here's the cheapest current price for the A.M.P. Gain
I've only purchased one thing from nothing but software before, and had no trouble with it, but I would do some research before buying. Their price of the A.M.P. Gain is a really great deal (enough for me to consider getting one, even though I don't need another dongle).