Yep, they are 64 bit.
I've read around and it seems the Penitum 600 series really aren't a very big improvement and are overall a pretty big disappointment, you won't notice much of any difference from what you've got so I'd suggest you stay put.
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