Opinion needed, re: Mass Effect 3 add-ons

Just got a $20 credit from the Playstation 3 store. Yay! I'm going to use it to buy some Mass Effect 3 DLC, but I need opinions on which to purchase.

My options are as follows:

• The Citadel DLC
• Omega DLC
• From Ashes & Leviathan DLC together

Thoughts? 

Oh, also I am through the ( cut for Mass Effect spoilers )