As I see it, and I'm not alone, the only way to accomodate high-heat overclocked hardware and relative quiet is to start with a low restriction case. This allows for quiet low power fans to move enough air to keep things cool.
I have an Antec sx1030, the sx830 is very similar. Other cases that would appear to be likely candidates include the Fong Kai FK320, the Lite-On FS 020, Chenbro Genie Jr., and anything else that has obvious open airways. These are generally larger cases, not quite full towers. It's a tough feature to find in a smaller case, unless you are willing to do mods.
Having a temperature-controlled fan on the psu is desirable. The Antecs have it, as do the Enermax 285 and up series. The antec 300w is at the top end of ordinary units, the Enermax is definitely a cut above if you are willing to spend the extra.
For case fans, the L1A series panaflos are among the best in terms of airflow vs noise no matter the size. They also work at 7v, in the event that you find that you can cut back on airflow.
For cooling the cpu, the Alphas are still among the best compromises when fitted with a 60mm fan of about 21-23 cfm. The Taisol 733092 gives very good results for a bargain unit, but is somewhat louder.
So far as sound-deadening goes, it can help, if only a little. Better to keep it quiet in the first place.
Where to buy- 2cooltek, Teamawe, Onvia, Mwave, Computer123 has good prices on the Enermax 351.
Just one guy's opinion.