The Roman general Thrifticus once famously said that if you can lead an army to war for $15 less than the current advertised price on Steam, you would be a fool not to take advantage. Really, look it up. What do you mean "The Romans didn't use dollars?" Stop asking so many questions, jeez. Bottom line: You can pre-order a Steam copy of Rome II on StackSocial for $45 . The historical accuracy of the preceding claims has no bearing on the deal.
The deal is available through July 15, and upon consulting the oracle, we've determined that you're not likely to be able to get the game this cheap again until it's been out a good long while. You'll need to create a StackSocial account really quick to complete the offer, but we promise, it's not one of those "Sign up for six credit cards and we'll send you an iPad" things. [We get a cut of each StackSocial sale, but you get your game at a quarter off the current price on Steam. Unlike the actual Roman era, everybody wins. - Ed.]
Also note, as per the terms of the offer, there can be no refunds. So make sure your system is up to spec to run Rome II's epic battles before cashing in. Update: This offer does not include the Greek City States pre-order DLC.