500w is plenty, if it's a good, high quality unit. 450w would actually be plenty if it was a top shelf power supply.
No, 4+4 is not the same as 8 pin PEG/PCI (For graphics card connection). Those are either six pin, or 6+2 pin, or in some cases there may be strictly 8 pin connectors on high powered models, but don't confuse them with the 8 pin/4+4 pin EPS motherboard power connector.