Hello.
I’m evaluating the possibility of buying a single core cpu because many “non-threathed” tasks are taking forever in some large scenes.
Running some maxscripts is becaming a pain because dual core cpu will use only core for these…image processing also can be very slow on large maps.
I didn’t searched for benchmarks yet but some tips about this issue would be great.
Thanks 
i have had some really good results with my centrino laptop. Aura simulations were much faster than my dual xeon 3.4. Other sim programmes like realflow were fairly quick on the centrino.
This probably isnt the answer your after but its a start!
The AMD Athlon FX57 is probably the fastest CPU on the planet… core for core. It can also be overclocked very nicely for an extra boost.