I guess the first questions to ask are - what exactly are you doing with the PC? FSX? Gaming? What is your budget? Do you want a new screen?
In my opinion, the best sweet spot in terms of budget is around $1500-$2000 because it will give you some of the fastest computer hardware that should run FSX extremely well, while also being very good value. A hugely more expensive computer isn't going to be much of a help.
SCREEN:
A big beautiful screen (>21.5 inch) is an absolute must, running at a resolution of 1920*1080 or 1920*1200 or above. I don't know much about running multiple screens so I cannot help out there.
PROCESSOR:
The best processor at the moment is the Core i7 2600. It is a 3.4ghz Quad Core with hyperthreading. The Non-disclosure agreement has ended so all the reviews have been released (e.g.
http://pcper.com/article.php?aid=1057&t ... ert&pid=14 http://www.anandtech.com/show/4083/the- ... 100-tested ) within the past few days, however they are generally not found in many stores. Wait a few days, or a week, and this will change. Anyway, the i7 2600 is based on brand new technology, so it should be very future-proof for well-over a year. It's the third fastest desktop processor in existence (the only faster ones cost twice as much). So anyway, it is excellent value for money, really fast, also has a very low power consumption. I highly recommend overclocking this processor because it's extremely easy and you can get massive gains from doing so - like 4.5ghz completely stable (whoa). If you plan on overclocking, make sure to get the Core i7 2600K variant, rather than the i7 2600. You can view performance per dollar, performance per watt, and a comparison with other processors in the PCPER review I linked.
Core i7 2600K is $317 (this one can overclock)
Core i7 2600 is $294 (this one cannot overclock very far)
Don't need to add extra cooling if overclocking, as the K model now ships with an updated cooler which is more than adequate.
MOTHERBOARD:
Motherboard, it depends on what you want really. I would expect the best to be ASUS ones and Gigabyte ones like the Gigabye GA-P67A-UD3R, GA-P67A-UD3P, ASUS P8P67 series. Make sure to look at the expansion slots and things like USB3.0, and E-SATA if you need those. Make sure the motherboard is socket 1155 for it to be compatible with the Core i7 2600 / 2600K, with the P67 chipset. I would probably get an ASUS motherboard simply because they have beautiful UEFI BIOS which looks nicer and should enable the computer to boot somewhat faster.
Motherboards are usually around $150.
MEMORY:
I rarely see FSX use above 2 gigabytes of memory although it does happen occasionally. IMHO you should get 4 gigabytes of DDR3-1600 with a CAS (aka CL) latency of 6 or 7 which should cost around $90. Alternatively you can get 8 gigabytes of DDR3-1600 with a CAS (aka CL) latency of 7 for $160. Make sure you are buying dual channel memory that runs at a voltage of 1.65 volts or less.
VIDEOCARD:
FSX does not benefit from dual graphics processors, hence it is best to get the fastest single GPU possible with the most video memory and memory bandwidth. The GTX 580 has this position although it is rather expensive @ $530. Could save a large amount of money by going with the slightly slower $350 GTX 570. Those are by far the best cards for FSX. There's also the GTX 480 which is the same sped as the GTX 570, but the 480 should be avoided since it is extremely power hungry, and rather loud. eVGA is a good brand.
For general gaming it MIGHT be a better idea to go with dual slower videocards, but this will perform worse in FSX.
relative performance:
http://www.techpowerup.com/reviews/ASUS ... 70/27.htmlperformance per dollar:
http://www.techpowerup.com/reviews/ASUS ... 70/29.htmlperformance per watt:
http://www.techpowerup.com/reviews/ASUS ... 70/28.htmlnoise:
http://www.techpowerup.com/reviews/ASUS ... 70/26.htmlHARD DISK:
Solid State Drives are by far the fastest drives on the market which means extremely fast boot times, quick application loading, and less (or no) stutters within MSFS. They are, however, expensive. It might be useful asking people how big their FSX installations are and then deciding for yourself whether you can fit it AND Windows on an SSD (they are usually 60 or 80 gigabytes). A better bet is dual 7200rpm hard drives, one for windows, one for FSX. Bigger usually means faster so get 1 terrabyte ones. Western Digital Black 1tb are extremely good, as are Samsung Spinpoint F3 1TB's.