Everyone's expectations are different, but here's what I have that works pretty good. H/P 8710 Pavilion, 450 watt power supply with an older AMD Quad 4 processer. Ati Graphics 2GB PCi Video (Upgraded from the original 1GB integrated), 2TB Solid State drive, (Updated from the original 1TB disc). This machine handles FS9 with all the sliders to the right without any issues.
I also have a Jetline Solo 900 machine for FSX but it's a BEAST and was a bit pricey. I don't fly the "X" sim too much. My FS9 has so many enhancements, (Scenery upgrades, both payware and freeware as well as additional aircraft). I think my FS9 install is "prettier" than the stock FSX install on the Jetline. JMO...
BB686