Doubtful you can hit 4ghz on a 680i motherboard. You'd need 500mhz bus speed(2000mhz FSB) for an E8200. The 680i is a good overclocker, but many folks find it hard to get to 500mhz bus speed.
2nd the E8200 typically max out around 3.8ghz , 3.9ghz. I've have yet to see a reliable E8200 overclocker reporting 4ghz. I'm not saying it's impossible, it's just very hard to do.
You should go ahead and Unlink your RAM, keep it at 800mhz. This way ram won't increase in speed as you increase CPU speed.