I am wondering what the lightest, double wall, expedition tent for two people on the market is right now, anyone know?

Far and away the lightest, double wall, two person expedition worthy tent is the Stephenson Warmlite Climbers Two Person Tent 2.33 lbs. http://warmlite.com/warmlite-climbers-two-person-tent. I have never used one, but have friends who love theirs. They have been used successfully on Denali and other nasty weather mountains.

I've had a Stephenson Warmlite 2R since 1973 and friends with a 3R since then too...no comparison for space for the weight...

Plus the catalogue is naughty =)

Another tent you might look at is the Hilleberg Nallo GT2. It is heavier than the Stephenson but has a really big vestibule. I know a couple people who have Nallo GTs and they are outspoken in their praises of Hilleberg (though perhaps they are just trying to justify to themselves how much they paid for their tents).