Lots of folks would recommend against mixing amd cpus with nvidia sli. Mobos/chipsets often act like Hatfields and McCoys.
Unless you have really special requirements, few folks here have ever recommended a 6-core over a good 4-core. The reason is almost nothing uses 6 cores, and most folks who have an important app or game are focused on that app or game, not running two or three of them at the same time.
If you don't currently spend a lot of time moving data in/out your system via USB 2.0, USB 3.0 won't be of much utility to you.
We are only now beginning to see SSD/mechanical disks sport SATA 3.0. When I look at my own needs, I don't plan to replace the HDs in my system during the life of the build, unless they fail. Your approach may vary.