Mostly gaming, web browsing,microsoft office etc..........
Except for gaming, I would suggest and Athlon IIx3 at most. But you need to tell me what games? What resolution? What settings? What FPS are you looking for? What video card do you have?
Information about bios flashing will be on the motherboard manufacturer's website under your model.
For most gaming, you will not see any difference at all from your current CPU. If you overclock, in a best case scenario, you are looking at a quad core 3.8GHz vs a 6-core 4.0GHz. Which I can't imagine making any noticeable difference unless you have 3 5870s in crossfire.