That's funny, I had the same thing, and upgraded the same way. I had e4400 and intel 965, and then got a MSI p45 platinum.
I can say it overclocked my e4400 to 3.2 easily. The same board overclocks my q6600 to 3.6ghz. And in researching this board, I saw folks with e8500 go well past 4ghz. There are a ton of switches in the BIOS for voltages, so it will be easy to get the max speed out of an older chip like e4400.