The Antec 300 is a pretty staightforward case. I like it better than any others mentioned so far.
1. The hard drive cage is a front to back configuration. Cables in some of the sideway configurations can be a pain in the butt.
2. The case is configured for a bottom mount psu with an air intake grill in the bottom case panel. My Corsair psu can be oriented fan side down to pull in cool air from below and exhaust warm air out the back of the case. The psu takes care of it's own cooling leaving case fans to handle the rest of the components. I made a custom pc stand so carpeting does not interfere with psu cooling.
3. You can configure the case for classic bottom front to top rear air flow using two fans in front and two fans in back.
I do not know if one of those big tower style heatsinks will fit in the case. Perhaps someone else has the answer.
I distinctly remember looking at the Antec 300 last year at Fry's Electronics while looking at cases for builds. I build pc's for friends, neighbors, and girlfriends. I wound up buying four of the Coolermaster Centurian 590 cases:
http://www.newegg.com/Product/Product.aspx?Item=N82E16811119152