If you’re considering upgrading I would suggest holding on a little longer. The first Service pack (or patch) for FS-X is in beta which suggests it will be release ‘soon’ and there will be further changes when the new version of Direct X (10) is released.

The simple answer to your question is that FS-X really needs the fastest CPU you can afford and at least 2Gb of RAM. Graphics card wise it would be wise to upgrade to a Direct X 10 compatible card. At the moment that would mean a NVidia 8800 based card which start around the £200 mark.

Rgds,

Bruce