The beamshots I've seen of the 816 are very floody - a large spread of light that will illuminate the hedge next to you as much as the road! (Okay, that's a
slight exaggeration... ) The 808E gives a beam with more "throw", if user comments are to be believed, so more light will be projected down the road rather than into oncoming motorists' eyes - provided it's angled down and aimed properly. I'm thinking about getting an 808E myself.
The asteri 6 would probably be fine at speed if you aim one lamp down close, say ten feet in front of you. It's close enough that you could just run it on the low power setting. Aim the second lamp further out and run it on high - that'll let you spot that pothole with enough time to avoid it!
I had a B&M Ixon IQ - in fact, I still have it. In pieces, in a desk drawer. It had a lovely beam pattern and was almost the perfect commuter light but unfortunately it's fragile - mine died after it fell off the mount (it wasn't clicked in properly, and the mount doesn't really give you positive feedback about when the light's securely in place). If they bring out a more robust version with more modern LEDs (brighter!) I'd get another one in a flash - if you'll excuse the pun