Thinking about upgrading my FS2002 system

Greetings all, Although my current system is a nice step up from the old Compaq 600 MHz machine, it's still not quite as fast as I'd like it to be. Pertinent specs as follows:Athlon XP 1600+512 MB ECC SDRAM18.2 GB 10K RPM SCSI HDRadeon 8500 64 MBThe usual assortment of optical and removable media drives...I like to run FS2002 at 1280x1024 with most of the settings maxed out, and in most places the frame rate is acceptable (18-25). Some places, like LAX, the frame rate drops down below 10 FPS. What's worse is when switching to external views on the PIC767, I can only expect around 3-4 FPS - unacceptable.I'm wondering what is the best bang for the buck - change to DDR memory (the MB does support it), swap the video card, or replace the CPU. In regards to memory, is there noticible performance differences between PC1600, 2100, 2700 (assuming my motherboard supports all these speeds). Or am I looking in the wrong place?Thanks any and all advice.