I tend to agree with uzi9mm, the XE Intel's use a Level 3 cache for the 2MB, which I have read is much slower (although still technically speaking very fast) than the L2 cache.
The newer 600 Intel's have the 2MB on their Level 2 cache, so they will generally run faster, and it makes their price tag cheaper. The 64 bit option is just the icing on the cake.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w