I was able to make this http://pcpartpicker.com/p/DHMfZL, there are some temporary discounts but when you're ready you can search for the latest discounts and adjust accordingly, it doesn't come with an OS sadly, it's a bit too much to ask for $400.
This model can be overclocked (yes that motherboard can overclock, but not through software) if that's your thing.
Also this one is the same but has an i3 and stock cooler
http://pcpartpicker.com/p/ZdVd23 which would be a little bit better.
If you're not really looking at upgrading much in the future I could have see what I can make with an AMD CPU, there's just less of an upgrade path with those
*Note: The case is more of a placeholder, get what design you like.