the CM 690 II is a great case for the money. The Antec 100 also has good air flow. You can try a 3rd party water cooler like the Antec Kuhler H2O, or a 3rd party air cooler. Gelid Tranquillo, Akasa Venom, Silver Arrow, although would be wasted on a value motherboard (since it will limit your overclocking anyway).
If you want a good airflow case, you can't beat a Silverstone Raven for its price. Plus, the RV02W-EW / RV02B-EW looks really cool. Also a Lancool PC-K62. There is only so much you can do to keep things cool, if your room / system temperatures are high. But we're talking 5-10C increase over a cool room, which isn't that bad.