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Amazon has pricematched the Steam Midweek Madness deal for the Dead Space games. Both are on sale.
I’m pretty sure you can activate Dead Space 2 on Origin. Not sure if Dead Space 1 can be activated yet or not.
Edit: Thanks to Alessandro for sending in this deal.
Man if only Dead Space 2 could be activated on steam! Dead Space 2 is on sale for 17.49 here in Australia compared with the 4.99 in US :0(