Bought a meter to check how much power my computer draws.
Overclocked CPU (i5-760), overclocked GPU (GTX 680), 4x DIMMs of RAM, four drives (SSD, Mech, Mech, Opt), keyboard with extra USB for USB-hub, mouse, external harddrive, wired Xbox controller, while charging phone, camera and headphone amp (Fiio e5) through USB.
Running Unigine heaven (realistic gaming load)
Peak from the wall, 317w. Non-bronze but 80+ PSU (first TX650). For simplicity, I'll take the 50% load number of 86% (230VAC).
So internally, it draws 272.62w (=42%), meaning I have roughly 377.38w to spare until I hit 650w internally - which it should be able to handle with overload.
Idle, ~91w (while all those peripherals and charging are plugged in). This is less than 20%, so its efficiency plummets below the 82% efficiency at 20%, but I'll take 82% anyway, and I get 74.62w, meaning it's close to approaching 10% draw idling, which is way too low.
In short, I need a bigger PSU so I can get more FPS.