I dont believe your going to have a problem. It takes alot of devices on a line to cause a problem.
Say your running a hard drive, a cpu fan, and 2 case fans on one line, thats not asking for trouble in anyway.
Alot of power supplies only give you two main molex lines, in which most people use the first for the optical drives, say you have 2. Then they use the next for the hard drive, video card and multiple case fans.
Most people do this setup basically because its the neatest, physically.
You would have to have a very large ammount of power sucking devices on one line to see a problem with your PSU.