This table came from Tweaker.net- she ain't in english, but you get the jist of 'er. That e6420 looks pretty sweeeeet- I'm assuming USD here.
ModelCoresKlokBusCacheNu April Juni VerschilCore 2 QuadQ660042,4GHz1066MHz2x4MB$ 851 $ 530 -38%Core 2 DuoE670022,66GHz1066MHz4MB$ 530 $ 316 -40%Core 2 DuoE660022,4GHz1066MHz4MB$ 316 $ 224 -29%Core 2 DuoE642022,13GHz1066MHz4MB $ 183 Core 2 DuoE632021,86GHz1066MHz4MB $ 163 Core 2 DuoE440022,0GHz800MHz2MB $ 133 Core 2 DuoE430021,8GHz800MHz2MB$ 163 $ 113 -31%Pentium D93523,2GHz800MHz2x2MB$ 133 $ 84 -37%Pentium D92523,0GHz800MHz2x2MB$ 113 $ 74 -35%PentiumE216021,8GHz800MHz1MB $ 84 PentiumE214021,6GHz800MHz1MB $ 74 Celeron44012,0GHz800MHz512KB $ 59 Celeron43011,8GHz800MHz512KB $ 49