The big advantage of the C2D is the SSE. K10 have better SSE ( full 128bits, C2D not all ).

if you disable the SSE on a C2D and a K8, K8 would be faster.

64bits mode use SSE, AMD don't loos too much here with the lot of GPRs in the K8. K10 will perform more fast in 64bits mode, with 8 more GPRs and double SSE.

K10 is a bit more fast in integer, but not a big improvement. about 15%.

Phenom will be a bit faster than barcelona clock for clock 8-10% i think, with 1066 non registered memory ( barcelona 800 registered ), and HT3 could be usefull for 4 cores.