I wouldnt worry so much about magnetism messing with the drive. The short answer is that those coils are chokes and wont have enough juice flowing through them to create any sizeable field. What I would worry about is
1. Heat. Those two devices right on top of each other are gonna generate some serious warmth. Make sure you have a fan blowing that heat away from there
2. Shorts. Make REAL sure that your drive is mounted very solidly and isn't going to jiggle its way onto the coils, or any other part of the power supply.