most of the speed test sites require flash but
www.bandwidthplace.com
works fine with the Fire. I was using the Silk browser.
As an update to my original, I was able to stream for a while last night without interruption so while the Fire does seem to have a weaker signal, I'm going to blame the choppy video the other night on my "only game in town so our service is weak and you can't do anything about it" provider.
