The most important things that you need to buy is power supply (PSU) to keep your system healthy and works fine. Because a system with bad psu is like a trouble maker kids
And dont forget to pick a reliable product from a major brand PSU because they wont be bothering you in the other time
Dont forget to look at 80+ gold sertificates and active PVC to get a better energy efficient and keep your monthly electricity bills low.
The second that you need is Heatsink Fan, Pick one of this :
Xigmatek HDT1284 or Cooler Master 212+
Thats a great HSF based on price/performance or something else that have better performance based on how much money that you need to spent.
Why you need This thing? To keep your system run in a cooler temperature and run in silent.
If you run your system only in 19" LCD thats vga is not a wise choose i suggest you to pick 6770..
But if play high definitions game in more than a 19" LCD, i think u need to pick 7950 or 6970 because this two things offer you better performance/energy and price/performance..
Optical is good and so on with the hard drive that you pick. Choose which one that offer longer guarantee