Thanks for the details Tony,
Sounds like you currently have a really nice FS9 setup!
So a couple things on FSX multi monitors, I run win7 and when I had a 3rd video card connected FSX would just crash. I am unsure if thats a FSX issue, or win 7 issue to be honest. I ended up removing the 3rd video card and used a matrox dual head to get around that issue. Heres a good read for ya on this subject:
Realtime Soft Forum
I am also concerned about your processor, FSX will run on that, however when using multi monitors in FSX it really becomes a CPU hog. I run a AMD 8320 (overclocked to 4.8Ghz on liquid cooling) and FSX still wants more power (granted I have a highly modified FSX install, with many addons).
I would recommend the deluxe version of FSX if you decide to purchase, as this includes service pack 2. Also I would highly recommend reading this article, following these steps will really enhance your FSX performance:
SETTING UP FSX and HOW TO TUNE IT - SimForums.com Discussion
As far as saving flights, you can defiantly save flights in FSX. However its a little buggy with multi monitors. If you are trying to save a flight so all your panels and views populated in the right places you have do it in a weird way. Basically you need to switch to windowed mode, undock your windows, place them where you want them, then save the flight. Switch back to fullscreen mode and load the flight and you are all set. Once saved in this manner it should load properly going forward provided you are in fullscreen mode when loading the flight.
If I were you, I would go ahead and get FSX, and give it a try on your current setup and see if it likes your current monitor setup, and see how it performs on your PC. More than likely you will have to edit your fsx.cfg file to squeeze every ounce of performance you can get. Heres a tool that does the main tweaks automatically -
SETTING UP FSX and HOW TO TUNE IT - SimForums.com Discussion
I think this is enough info for now, but If you do get FSX and have any questions or issues, feel free to PM me here, I'd be glad to help a fellow simmer.
Thanks,
SimAviator13