Importance of Northbridge and Southbridge??? Quality PSU?


Baseband Member
Alright, even though I'm trying to keep up with posts and updates as much as I can there is SOOOO much going on it's almost impossible to keep up. I'll update my final build later, but I'm going to ask a few last questions and hope you can answer it to help me decide what I'm going to get.

Seventeam Quality PSU? If so I can save money and get a modular PSU which is pretty nice.

What's the importance of the Northbridge and the Southbridge?
The motherboard I chose has an AMD 770 Northbridge and an AMD SB710 Southbridge. However, I can upgrade my motherboard to an AMD 870 Northbridge and an AMD SB850 Southbridge for about $40-$50 if its going to be worth it. This upgrade would also give me a USB 3.0 instead of USB 2.0.

This website gave me a formula of how fast your North Bridge should be to keep up with your CPU.
Northbridge Frequency (+/-200) = (CPU-Frequency * 2 ) / 3.15

I understand that this ratio is used for overclocking. However this still means if your Northbridge wasn't fast enough your processor would suffer. Is the Motherboard I chose with an AMD 770 Northbridge going to be able to keep up with an AMD Processor 3.4 GHz? Or should I upgrade to the Motherboard with an AMD 870 Northbridge and AMD SB850 Southbridge along with the USB 3.0.

Any recommendations on cases?
I have looked through a lot of cases and I can't choose, whenever I find one I like I read a review saying how much is sucks. I just need a case that will not interfere with my audio, it has enough room to fit all the hardware in, and it has good enough air flow to keep the system cool.

Again, thanks a lot for the help everyone. A few days ago I knew absolutely nothing about computers, and I've come a long way. I ready everyone's comments and have been taking my time to research based on your responses. I hope I'll get my final build up soon and be able to order it by next friday.