Do i need more power with HP m8120n and a GeForce 8800 GTS 320mb vid card?

Hi, i just got a HP m8120n with the quad core processor. It has 3mb ram and the one upgrade i made from the beginning was changing the vid card that many online suggested. I installed a EVGA Geforce 8800 GTS 320mb overclocked vid card.

The EVGA min requirements suggest a min. 400 watt power supply but the HP comes with a 300 watt power supply.

My question is, do i really need to upgrade the power supply? i dont have many other peripherals except for a printer installed.

Thanks.