Yeah, that'll do it, always change the auto setting. But note that even without raising the voltage, you're feeding more power to the processor. You cannot raise the clockspeed without raising the voltage, and that's why your temps will rise even when you keep the vCore at stock.
Personally, I think 2.4Ghz is complacent for an E6300. Try for 2.8Ghz, max out that DDR2-800 with a 1:1 ratio, and then start testing from there.
And don't worry about temps. Load temps in the 60°C-65°C are not uncommon with Core 2 Duos, and as long as they don't break that range, you should be fine. Also, remember to use an aftermarket cooler and Arctic Silver 5 if your temps aren't to your liking.