edit: Saw that you were a 'maybe' for crossfire. If you think you want to crossfire, and want to budget for it now, the second PSU (Seasonic 620W) is a better choice than the OCZ because it's got more 12V output (combined 576W and 24A max/rail, versus the OCZ's 552W and 25A max/rail), and it will be a higher quality supply overall. However, I would consider going for this if your sure about doing crossfire http://www.newegg.com/Product/Product.aspx?Item=N82E168.... The 620W is probably fine, and is better than the OCZ 700W, but the Seasonic 750W will definitely be solid for two 7850s.
Theres about a ~10% difference clock for clock between the generations. The 3540 won't really be that big of a deal, either is more than enough for gaming though. Also, the case you chose is very nice.