Non-OC'd, you'd only expect maybe a 35% CPU speed boost with the e8400, and I don't think that would be very noticeable to you. The really good OC's of e8x00's come from FSB's in the neighborhood of 1600MHz or more, and your older MB is going to have a hard time with that. If you go with a new CPU, I'd get a new modern MB at the same time (with something like a P45 chipset).