8" disk drives and modern PCs

I have a qustion about powering the 8" disk drives I have connected to my disk duplicating computer. Specifically, what is the "best" power on sequence? The drives I use are the Tandon TM848-2E. It requires 24V @ 750mA and 5V @ 450 mA to operate. Pretty easy so far. I use an external power supply to power the drives. I want to add a relay powered by one of the diskette drive lines from the standard PC supply to turn this power supply on. Again, faily simple. My question is what is the best order to turn things on. I've always turned the drive on before powering up the PC, and turned the drive off after powering off the PC. Does this really matter? I always make sure there is no disk in the drive before doing any power cycling. To simplify matters, I could always just put everything on one big switch on the mains. You know, like using the power strip to power on/off. Any opinions about this? Any suggestions? Thanks, Kelly