I am using an i5-6500, an r9 380, two 4gb sticks of RAM, an SSD, and an HDD. What wattage of PSU do I need?
I would recommend the EVGA GS, G2, or GQ.
Depends on how much your budget is.
What is your budget? 550W will do absolutely fine. I'd recommend a 550W GS/G2/RMx or a 650W GQ/Leadex, whichever is more convenient.