The i7 3820 -
http://ark.intel.com/products/63698/Intel-Core-i7-3820-Processor-10M-Cache-up-to-3_80-GHz - is NOT a "K" series processor, and is therefore NOT a recommended processor for FSX or X-Plane.
As I've said, the highest possible overclock is absolutely critial to achieving the highest frame rates. As you can see in my signature, I'm running an i7 2700K overclocked to 4.8Ghz, which is ideal for FSX as well as X-Plane.
Also, since the i7's have Hyperthreading, they maintain a higher
minimum frame rate at the same clock rate than their corresponding i5 equivalents. Further, the 3820 is a 130 Watt processor, which is more difficult to cool than the 95, 84 and 77 Watt i7 and i5 variants. Nevertheless, high-end air cooling or liquid cooling will be necessary for a high overclock.
Other cooling concerns are that when selecting a graphics card, consider that cards which exhaust all their heat out the rear of the case are preferred over cards which partially exhaust or recirculate all their heat inside the case.
You appear to be inclined toward purchasing a pre-built system, rather than building and overclocking your own rig (highly recommended). You also seem to be interested in a 5 display system, which is unnecessary and impractical.
However, if you can find a system builder who will build to your specifications, AND if you're OK with the fact that it would cost much less to build your own, then I would recommend the following guidelines upon which to configure a custom pre-built system:
(1) CPU - Intel i7 4770K overclocked ~ 4.4Ghz (latest generation).
(2) GPU - EVGA GTX 760 SC 2GB (latest generation).
(3) Memory - 16GB DDR3 1866Mhz CL9 (=>12Gb no Swap File needed).
(4) SSD - 256GB Samsung 840 Pro (fastest Windows and FSX load times, smoothest FSX scenery transitions).
You will also need a good socket 1150 / Z87 motherboard designed for overclocking, such as the ASRock Z87 Extreme6.
Hope this helps,
Comp