What is the best shield for an uber conc barb?

SS socketed with 40/15ias (what is the 40 for??)

or

Phoenix Monarch.

Edit: How much is a 40/15 alone and in the ss already? Also, do you have any or know of anyone who has some ft?

SS
40/15

40= 40+ enchanted damage
15=15+ Increased attack speed