Asus boards are good....Again look for either P35, P45, x38 or x48 chipsets...Each are very good...
Yeah the chipsets Hellsent layed out are pretty good, there are many cheap boards out there from reputable brands i.e. Asus, Abit, and Gigabyte for example.
Don't forget to Install at least Vista Home Premium so you can take advantage of the 4GBs of RAM as you will need it.
Are you getting the Deluxe Edition?
I'm not sure what version of FSX, this build is for my uncle.
Lots of asus p5k's to choose from. I probably wont use integrated wifi though.
Although now my interest has peaked in looking at the Radeon HD 4870. I need to look into some benchmarks for that though, as FSX is mostly CPU.
fsx directly renders every frame. the only way m.s. could have optimized any more poorly would have been to scan each scene and converted them to a series of bitmaps that flip out in front of you, cartoon style.
as far as your mobo, i wouldn't hesitate to reccommend an asus p5e. it runs cool with all the rollercoaster heatpipes going everywhere, and it's very well laid out. i was able to install a thermalright sp-128, but i had to do it with the mobo uninstalled, and even then there were some tense "how much more pressure can i apply before i warp my $130 board" moments. excellent overclocking options, and it even came with a discrete audio card, though one on par with a creative extremeaudio, meaning it still uses cpu cycles (though that's less of a problem these days with multi-core fast processors).
one more thing i like about asus--the fit and finish. i think only gigabyte with their "ultra durable ii" series uses thicker silicon. you also get case connector stand-offs so you can plug in all your case lights/pwr/rst etc into a clearly labeled standoff that then plugs directly onto the mobo, saving you the trouble of having to emply any guesswork as to how the Taiwanese have arranged their case inputs (something about living backwards from folks in the western hemisphere :P ), along with all sorts of extra cables and stuff for the crap drawer.