[Blind-sysadmins] determing pc power needs?

Hello, This one is for PC builders. I've been gathering parts mostly in the last month for a new PC. Currently I have a Gigabyte 970 USB 3 motherboard, 32 GB of ddr3 1866 ram, and an 8 core processor that part alone I know takes 125W of power. Ok, the power supply will need to be an ATX12V supply I've found two on newegg I like one for 500W the other for 530W both around the same price. My problem is determining my current power usage needs, currently I'm guessing, and future needs. This box will eventually have all six SATA3 ports used, one CD/DVD burner, one SSD drive, and four 7200 RPM SATA3 drives 1 TB or greater. Opinions on power? Also, SLI and Crossfire ready do I need to worry about those? Thanks. Dave.