If no monitor upgrade, 1800 is more than enough. Above is right, 700 PSU is too low. Need at least 850 nowadays, IMO. And clean, stable power is very much worth it. So get those 850 Gold PSU. Cheap ones tend to have problems later on and it is not very obvious for you to diagnose (it leads me to think my MOBO or Graphic cards are dying when it constantly tries to reboot).

If you don't buy crazy input devices (200 dollar keyboard, 150 mouse, etc). $1200 is enough to build it.

I do think not need to upgrade in 4 years is a bit of stretch though. You gotta at least upgrade graphic cards in 4 years to keep up.