Inkmoth Nexus would be perfect, if I had any. I would love to get a set of four but they are just very pricey at the moment. With good reason, though. I was using Virulent Wound to help with creature killers but more pumps could speed it up more. I'm just worried about the opponents defense.
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Also, since your using Shirei, Shizo's Caretaker; I would ad one more, maybe two more, and then add some Bile Urchin in there - four if you can. That is also a great combo. Kakusho would help some two since you could take nine life and gain the same from someone just using that card and Devouring Greed. However, I got rid of Kakusho and my deck still does fine.
Also, I would get rid of Mirror Gallery. You only need the Inames for their effect and using more then one of the same is something you really don't need. Replace them with Grave Pact. I just got some of these and am adding them to my "Iname as Greed" deck. Trust me; using this card with devouring Greed to gain health, deal direct damage and getting rid of your foes creatures is an awesome combo.
My first deck I posted a wile back was something like this. Iname as Greed http://www.mtgvault.com/viewdeck.php?did=4059