Do yourself a favor and keep them. Theory11 does not sell them anymore. They are a collectors item, sure you can use them. But why would you want to do that? They are nice cards. Keep them in the cellophane and put them up on your shelf to show off.
Plus, if you did try to sell them. I'm not even sure it would be worth it. Sure, you could get a couple more bucks then they are sold for. But, like I said, I would keep them if I were you. Maybe I'm wrong and they are worth more then I think. I still think you should keep them.
Those are my two cents. Take and use them as you please.
~blake.