I don't like heat cable,I don't think that it is any safer than flexwatt. AP makes good racks as well.

I feel that buying racks is worth it, they last longer and are built better (by computer controlled machines) They cost more upfront, but the fact that they are enclosed (except Visions which I'm not a huge fan of) means that they will hold in heat much better. If you do decide to build one yourself, I would link into building a frame, then enclosing 3 sides with a good insulation