Help with Components

Im looking to upgrade my PC I don't want to spend more then $550 Roughly = ZAR4000

These are the components that i want to purchase.

1. ASRock Z68 Extreme3 Gen3
2. i5 2500K
3. Corsair CML8GX3M2A1600C9W Vengeance LP 8G

Im doing this upgrade bit by bit. I already have, in the past purchased an Antec 300 case and a Sea Sonic S12D-750 Power Supply - 750w, and I currently have a ATI 5770 (this will be the last component that I upgrade in the future)

What i want to find out is, is this a good choice of components or are there others that i should be looking at (Is this a decent choice)?