Go for a E6300 - it's $50 or so cheaper, and you the amount of speed you lose won't be noticeable; if you're desperate for that speed, you could overclock it that tiny bit higher easily.
The extra money would allow you to get a decent motherboard - Core 2 Duo motherboards, at least the good ones, aren't cheap, and you really don't want to be skimping there. It's much easier to upgrade the CPU than the motherboard, so paying that bit more extra will set you up in the long run.