FSX has been out long enough that the hardware has caught up a bit.
Almost any modern box will run it fairly well as far as default, and
not a bunch of add ons.. Heck, I started out on FSX with a single core
P4 at about 3.0 ghz. That was using a Prescott 2.4 ghz CPU and over-
clocking it..
Right now I'm using a fairly cheap rig money wise..
It's a Phenom 2 555, that I unlocked from a dual core, to
a quad core, and also overclock it a bit.
It's not bad at all, and I'm just using the cheap onboard video,
which is a ATI HD-4200 with 768 MB video ram.
I only paid $115+tax for that motherboard and CPU. I'm using
4 GB of DDR3. "I'm using a AM3 MB".. Ram is much cheaper now,
than when I bought that, so I'd probably go 8 GB, even though XP
can't take advantage of it.. It would help if I switched to Win 7.
Anyway, it's quite usable for a cheap rig, and I usually run the
737 NGX, which is pretty demanding on the CPU.
It would be better if I got a better video card.
If I were to buy a box right now, it would most likely be a
i5 2500k, and I'd hot rod the snot out of it.
It would be noticeably better than the Phenom 2x4 I think..
But a bit more $$$. About $265+ for a MB and chip, more if a
higher end MB.. But hot rodded, and a good video card, that
rig can kick some FSX butt without breaking the bank.
Course, I'm talking building it oneself.. I build all my boxes..
The only one I ever bought turnkey was my first 386/33 DX I got
in 1992. That was my first "real" puter.. I had a IBM 8088 rig,
but it was useless for most stuff.. Pretty primitive..
You couldn't run FS4 on it, that's fer sure.. :/