Make sure your BIOS is updated to make sure the CPU support is in the system before upgrading.
CPU:
http://www.newegg.com/Product/Product.a ... 6819115036
That one will do 4+GHz on the right air cooler
Or this one a few bucks cheaper may have more trouble reaching 4 but it will do 3.6-3.9 no problem
http://www.newegg.com/Product/Product.a ... 6819115037
Memory:
2x2GB DDR2 800 4-4-4 timing
http://www.newegg.com/Product/Product.a ... 6820231209
now those will allow a great clock however for bleeding edge clocking, these:
2x2GB DDR2 1066 5-5-5 timing
http://www.newegg.com/Product/Product.a ... 6820146785
You will have to clock the motherboard to use either one. A 400Mhz FSB (minimum) will be required.
A E8500 has a 9.5 multiplier ability.. 400x9.5=3.8GHz, set the CPU STRAP to 333 for a DDR2 800 mem-speed..
For the E8700 it has a 10.5 multiplier which means 10.5x400 = 4.2GHz
Both require proper cooling solutions as you will need to raise the CPU voltage to do any clocking above 300-500MHz+
As you increase FSB the mem-speed available will increase so in the case of a bleeding edge clock you need the 1066 memory. If you do not intend to try and push it to the max the DDR2 800 memory is fine but you do need to make sure both the memory speed and timing are right after installing the memory.
Now, the issue of 4GB.. you can use 4GB of memory and those big planes can use the extra in FS9 as long as you manually edit the FS9.exe file to use the LARGEADRESSWARE flag and also set WindowsXP/Vista x32 up to not have issues with >2GB. In the FSX forum at the top of the list you will see my tuning thread.. a few posts down directs in how to set Windows up to work with >2GB and not throw out of memory errors.
The process for making FS9 >2GB aware and use it is here:
http://www.ntcore.com/exsuite.php
Make a backup of the fs9.exe file in the main Flight Simulator 9 folder and place it somewhere safe. Using CFF Explorer browse to fs9.exe and open it in the application. (FILE