Thanks! Yeah - Apple TV works, Amazon Prime and Netflix both work in Chrome and Firefox. Neither work in Safari (Safari asked to install Silverlight for Netflix, which I didn't do, and it was just unsupported in Prime).
One thing that I'm fairly disappointed with is just how hot and noisy the card runs under Windows in pretty regular games, or even just the Time Spy benchmark. 70° main temp and 110° hotspot/junction, even with an open case...
EDIT- Turns out the card was the issue - I exchanged it for an another identical 6950xt and it works far better + cooler. Hotspot temps hover around 90°. The first reference card I had probably just had poorly applied thermal pads or something.