When dual wielding daggers, I have found I am unable to attack with both weapons and get the dual x30 damage from both daggers (Shrouded Gloves, Assassin's Blade). I seem to remember reading somewhere that when you attack with a single dagger for a sneak attack when dual wielding, the damage of both daggers applies to this single weapon attack. Is there any truth to this, or would I be just as effective using a single dagger and saving the use of my off hand for a spell or something?

Here's the UESPWiki write up: http://www.uesp.net/wiki/Skyrim:Sneak#Sneak_Attacks