hi! Basically i'm looking for some recommendations on Passive CPU cooling or CPU Coolers that are extremely quiet yet high performing,

The case used has the airflow from the two fans near the CPU blowing out. It is the Fusion 430 black with an AMD athlon 64 X2 4850E Brisbane. Building a home theatre PC.

Any suggestions will be appreciated. Thanks!

The Cooler cannot exceed 14,5cm for height.

I looked through the reviews for that case on NewEgg, and one person said that they were using a "Scythe Mini Ninja Passive." Apparently it's this one, but without the side fan put on.

That case's fans are close enough to the processor that you should be able to use a number of different heat sinks with it, and just take off the fan. Keep an eye on the temperature though.

I'm using an Ultra-120 eXtreme with a Noctua NF-S12 1200 RPM case fan. And its DEAD quiet. And the Noctua pushes out a shit load of air, it always running at 1200 RPM, and I can barely hear it - seriously. However the Ultra-120 eXtreme at it's tallest point stands at 160.5mm.

I would suggest at looking at the Noctua NH-C12P kit (tallest point + fan is 114mm).