DMU and the Caching process can make use of multiple theads as can the FEA mesher & solver. I have a recollection that the MC'in workbenches do but I am unsure.
The rest as far as I am aware in uniprocessor.
However, I am a fan of SMP / dual core machines as they enable you to still be productive (on some other task email, calcs, etc.) whilst Catia has tied up one processor /core thinking about something hard.
In the windows SMP world you do not need as seperate graphics adaptor one will be fine.
There are different ways of implmenting SMP at a board level as far as I am aware intel use a shared memory model (both cores address the same memory through the same bus) where as AMD has seperate memory buses for each core. But it is a while since I took an active intrest in achitecture so I could be wrong with current processor.
Dual 64 bit processor will be treated in the same way dual 32bit are. Again as far as I am aware hyperthreading is a additional CPU instructions for assisting in the priotising & processing of other CPT instructions.