It looks like it doesn't matter whether you're encoding audio or video - the e6750 will be about 50% faster than the e4300.
Different codec, but the same story. The percentage performance difference between DivX and Xvid encoding is negligible.
It's beginning to sound like a broken record, but the magic 150% number keeps showing up. It's no surprise that the e6750 truly looks impressive compared to the e4300.