Ok so i recently went out and bought a new video card cause my computer only had onboard video so i got myself a Sapphire HD 2600 pro, now my problem is on the box it says it requires a 400 watt power supply, but my power supply is only 220w and the power supply i bought doesnt fit in my case (XCCube T_T) now my friend said it would be fine with just the 220 watt PS but im not sure, what should i do?