MrHawk, do you need OS and monitor?
You can easily get a great system for $1000, but you can also get an incredible system for $1200. Decide on a price, and then realize you'll probably spend a little more than that cuz people tend to want more. Do your best to stick to a budget.
I must add, if you are ok with Medium to High, then you can easily do that with those games at $1000. Just tell people what you have and need.