See if this helps.
I'm thinking of building a new system, but I love the case and power supply that I have (Antec 430W). I'm thinking getting an A8N-E motherboard, Athlon 64 3500+, possibly a GeForce 6600 or 6800, two SATA hard drives, a wireless NIC, a floppy drive and a DVD burner. Will a 430W power supply be enough for that? And is there any place I can go that would help me calculate some of this stuff?