With the speed of today's processors, you will not notice much of a difference in just a few hundred MHz upgrade. That is why I am going for the Athlon 3200+ which is much cheaper, because the 3400+ wont give me that much of a performance boost over the 3200+. However, with more RAM, your computer will run much faster because it will not have to use the page file as much. Hard drives are slow compared to RAM, and when your PC is using the page file too much, its not fun. Faster RAM will also mean faster performance. Always go with the speed that matches your front side bus, NEVER lower.