Today's a good day for picking up a new PC game! Space strategy epic Sins of a Solar Empire: Rebellion and post-apocalyptic action-RPG Krater have both just released on Steam for your consideration. Check out trailers and early impressions below, and let us know which you're planning on playing (or both, or neither).First up is a new stand-alone expansion for the space war real-time strategy game Sins of a Solar Empire, Rebellion. I've been playing into the wee hours to crank out our review, and my early impressions are it's at least as much of a blast as the original. Massive Titan-class ships and a major rejiggering of the tech tree keep things interesting, and the pirates have gotten an upgrade to the point where they're a real threat. (I'll have much more to say about it shortly.) My only real hangup is that it's currently twice the price of Sins of a Sins of a Solar Empire: Trinity on Steam, and it's nottwice as good. If you like Sins' brand of real-time strategy with a healthy dose of eXploration, eXpansion, eXploitation, and eXtermination (4X), though, it's a safe bet. If you don't know yet, you can get an idea with the original Sins demo. Also making its debut on Steam is Krater, an post-apocalyptic dungeon-crawling action-RPG from Swedish developer Fat Shark. I've only played the pre-release demo version so far, but it has some interesting ideas about multi-character control and crafting that make me curious to see how it all comes together. At $15 you can't go too far wrong, but be advised that the online co-op mode doesn't currently work -- that'll be patched in later. If you're feeling burnt by Diablo 3's always-online setup and constant nudging to play with others, this might be a pretty good option for you. Check back later this week for an update on that one -- we'll have our review up ASAP.What do you think? Planning on picking up one or both? Let us know!