I have a m17xr3 I use for FSX, most of the time I am fine running FSX, but after installing new scenery, and a buildup of tons of a/c over the years FSX really drags my system down especially over heavily populated areas.
My current spec is;
580m card, 16gb, 2630xm processor, 500gb 7200rpm raid 0.
I was weighing the options of upgrading to a newer processor and switching to ssd but figured I could use a new computer. Don't have a ton of money to throw at it, but I put together a computer online;
CPU: Intel® Core™ i7-4820K Quad-Core 3.70 GHz
HDD: 250GB Samsung 840 EVO Series SATA-III 6.0Gb/s SSD
MEMORY: 16GB (4GBx4) DDR3/2133MHz Quad Channel
VIDEO: NVIDIA GeForce GTX 770 4GB GDDR5 16X
I don't care about sli, and I know fsx likes nvidia, as well as high processor speeds and doesn't take advantage of multiple cores anyway, so I should be fine with this slower 4core.
Add a name brand 1,000w (or better) power supply to it.
I really need to make an actual account. The guest rigamarole is killing me.
Just had to throw a couple pieces of knowledge that I've acquired through my own building experiences.
~Don't get the 4GB 770 unless you are running multiple monitors, or using some oversized display like a HDTV. FSX won't utlize more than 2GB of VRAM on a single display.
~The Ivy Bridge is fine, you are correct in FSX being more CPU intensive. You picked a "K" series, so it would be in your best interest to pick up a water cooler to support the overclock if you desire to do so.
~You hardrive is a little short on capacity by modern standards, I understand it's a SSD, which is awesome, I preach the benefits of SSD's all day long, they're just too damn expensive. You may consider though, try getting a normal 7200 HDD to supplement it. A 1TB HDD is actually pretty inexpensive, and you can use it to store media and whatnot, saving the SDD for your OS and games like FSX.
~If Radeon is your flavor of choice, go for it. FSX will run Nvidia or Radeon equally. I just prefer Nvidia due to brand loyalty, and I find it easier to tweak.
I'm done, good luck.