DFI recommends a minimum of 480watts for the lanparties just for stability reasons running at stock speeds, of course you can get away with less but better safe that sorry.
The problem with the DFI JP17 is the fact that is switches from the 3.3v rail to the 5v rail and leads to increased instability. Of course there is the jumper mod I was talking up which keeps the vDIMM specifically on the 3.3v which reduces all these risks and I would recommend doing if you are setting the jumper to 2-3.
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