Generally speaking:

• CPU: Yes, the faster the better. Multiple cores, however, are only used if you explicitely use parallel processing in the workspaces. Otherwise a very fast dual-core CPU is king.
• RAM: Yes, but it depends on your data volume. Unless you do crazy stuff you'll get really far with 8-12 GB of RAM and 64-bit FME. Just check in your FME log that there are no messages about optimizing memory usage, which is a very bad sign.
• GPU: FME cannot use the GPU at all, so save the money for something else.

One thing you didn't mention is disk, make sure to configure SSD storage with high bandwith. The faster the better, as FME has a tendency to use a lot of temporary storage.