3ds max 7 and Maya
Unfortunately, the 2.8GHz frequency of Athlon 64 FX-62 processor is not enough for successful competition with Intel Pentium Extreme Edition 965 during final rendering in 3ds max 7. The thing is that rendering can be split into a few parallel processes easily so that all four virtual cores of the Intel processor get loaded to the full extent. However, the situation is different during final rendering in Maya: the high-end dual-core AMD processors are ahead here.
As for the benefits of DDR2 SDRAM, we can state that there are none, or there is even negative influence. Anyway, final rendering is not the reason for you to switch to the new AMD platform.