Multi-threading focus
Multi-threading: Cinebench 2003, MainConcept MPEG Encoding, 3DSMax v6
Cinebench 2003
Using the multi-threaded CPU test in Cinebench, which uses one thread per processor to speed up a scene rendered using the Cinema4D software renderer, you can see the increases a multi-processor system can give you.
Using two render threads, the X2 has nearly twice the performance of the FX-53, and itself when running a single thread.
MainConcept MPEG Encoding
I use MainConcept's MPEG encoder to transcode a video clip with larger than PAL video resolution, into standard PAL SVCD MPEG2 format.
Again, there's nearly a doubling of performance.
3D Studio Max v6 - HEXUS Superstress v2

The mentalray renderer which I use for our own 3D Studio Max v6 Superstress test is multi-threaded, but only in places, and not all of the composite tests are able to benefit. That said, the X2 is still usefully faster than the X2.
The 3D Studio Max v6 test highlights that software has as much to do with performance as the underlying hardware. Regardless of the theoretical ability of a computer system, it can only be realised by software which exploits it as much as possible. That happens in this test, but not to the degree it does elsewhere.