Thanks for the reply.  You confirmed my suspicions.  As much as I'd like to try the open cans, I guess it would really defeat the point.  Ordering 170s now!

So I'm another one who's trying to decide between the 170s and 180s.  I'm going to be using them for late-night movie watching in bed.  My wife's had it with me watching movies into the wee hours while she tries to sleep.  The big question is "will my wife continue to glare at me during movie...