Ahh. I've got that exact same CPU and similar RAM with an Asus P5E3 Pro, and for the price (about $100 less than the Striker II) couldn't be happier with the results. It supports everything you've got, the one drawback being that it doesn't do SLI, only Crossfire. So if you're planning on adding multiple nvidia cards at some point, you may want a different board. But if you stay with a single nvidia card, or switch to ATI card(s) for your next upgrade, it should be fine for you.
As far as a board that supports a Q9550, DDR3-1600, AND SLI, the Striker honestly looked like a pretty good choice, except that it was broken.