Where will you be buying from? By that I mean where do you live as I see you have put your budget in dollars. Dollars are used in many countries so it would be helpful to know where you are based which will also effect the exchange rate.
If your budget is in US dollars then you have plenty of cash for your PSU and GPU if buying in the UK.
It would be helpful to know your motherboard.SIW. Download and install the free version of SIW which will tell you everything you need to now about your PC.So you will get the motherboard info here.
Looking at your image I see that your PSU is a cheap 420W unit and I think that you have a pretty basic case. I would suggest adding a new case to your list. $800 is more than enough for a decent case,PSU and graphics card.
I await your answers to my questions.