CPU Upgrade?

Hello,I am contemplating upgrades to my ancient PC, and with the restrictions that are placed on possible upgrades with my current motherboard, I am trying to find out what I might be able to upgrade without doing a total overhaul. I only use FS9 about 1x per month, so it certainly isn't worth it to me to spend hundreds of dollars on practically building a new system.Having said that, I am looking at possible CPU upgrades that might be able to fit in my current motherboard; namely the 939 socket CPU. Being that FS9 is a more CPU centric program, I figured a dual-core might provide significant boost in performance compared to the minimal cost of the CPU.Does anyone happen to have any experience or thoughts on the CPU, as compared to the amount of performance one might be able to gain from upgrading from my current?My current specs:AMD Athlon 64 3500+ATI AIW X800XT 256MBASRock 939Dual SATA2 ATX MotherboardKingston HyperX 4GB PC3500Windows XPThanksMy current specs:AMD Athlon 64 3500+ATI AIW X800XT 256MBASRock 939Dual SATA2 ATX MotherboardKingston HyperX 4GB PC3500Windows XPThanks