The i5-3570K is a sound platform to build an fsx rig around but you need to get a dedicated video card. As !bluetonic! says fsx (as with fs2004) is largely cpu bound so adding a cheapish (£20-30) aftermarket cooler and overclocking to 4.2GHz for example will make an improvement. Traditionally in the past nvidia cards have performed better than their AMD counterparts but not too sure on how the latest generation perform. For around the £100 mark for nvidia cards you may be better off going down the route of second hand and picking up a GTX470/480/570 as the latest generation hasn't been refreshed as of yet. As for the red team, the 2GB 7850 offers by far and away the best bang for buck and also have massive overclocking potential but as mentioned before I'm not too sure whether the latest AMD cards have solved the shader problems of the past?