Hi newcomer and welcome to the Tom's hardware forum.
1- Solid rig
2- The speed isn't as important as the CL, so u can go with 1600 CL8 or better, remember that with a lower CL u get better performance. For example 2000MHz with CL9 isn't very good and usually is more expensive that 1600MHz RAM.
3- This G.Skill Ripjaws 1600 4GB(2x2GB) are very good.