Depends what you classify as a performance gain. Currently AMD holds the title of fastest single and multithreaded processors with the Athlon 64 FX-55 and Athlon 64 X2 4800+ (an opteron may be faster but I frankly don't know as they aren't compared as competetively as the desktop platforms are) in 32 bit enviroments, which I would consider a "performance benefit" if anything at all.
Since an Athlon 64 hasn't been given the ability to run in a true 64 bit enviroment it's real performance attributes are still unknown.
Regardless, it is still a powerful 32 bit processor platform, not to mention a cheap and flexible one at that.
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