upgrading from Nvidia 8400GS to Nvidia 8600GTS PNY

Hey, im wondering if any can help, i just got a HP pavilion elite bought a Nivia 8600 pny gts to install into it, though im playing direct X 10 smooth on low settings as is,, and i notice the wire that goes to the card a BLK n white double wire, from mother board isnt quite the end on it though theyre both double wire,,, seems to be aux power of some sort, can anyone identify this wire or end types ill need? , also the HP came with power supply 300w and Nivia says it needs 350 minimum,, well b4 i get looking for new power supply prolly a 350w being that iv heared thats all the mother board can handle (hp told me)
im wondering if itrs too low of power could it hurt something or would i simply not be getting max performance?

THNX in advance

Firstly i second the advice above, it's all good.

Secondly i would advise you to take back/send back that card and try to get your money back/some voucers. This is because you say you want to play DX10 games, the 8600gts which you have chosen has abysmal performance in DX10 games. I would recommend spending a little more on something like an ATI HD3850.