Lame 3.97 benefits naught from the change to four cores, the one-second difference possibly due to windows offloading some of its own background tasks to another core.
OGG shows zero difference between dual-core and four-core system performance.
DivX 6.6 is multi-core optimized, reaping huge rewards from the change to a four-core processor.
XviD doesn't appear to use the additional cores at all, yet better overall system performance still gives the current configuration a slight lead over its dual-core predecessor.
3D Studio Max is strongly multi-core optimized, achieving significant improvements from the Core 2 Quad of the current mid-priced build.