I was a bit puzzled by your question, and while you've had two good suggestions, let me ask a follow up.
When you say add the bench to your entertainment unit, are you sizing it to fit inside something or across something? Must it be precisely 60w and 10 h?
If you would accept less than five feet and something higher than 10 inches, then IKEA for example has some fairly cheap TV benches.
Your question suggests minimal or no woodworking skills and perhaps no tools. If that is true your options are to buy some basic tools and start on the learning curve, buy a premade unit or do something that a lumber yard or HD can cut for you.
If you use MDF or 3/4 plywood to make a simple upside down U shape, then as already said the 60" span will sag and unless you used large angle brackets with through bolts and nuts, it will be very weak if racked.
The PVC idea is interesting, harking back to the cinder block bookshelf idea. But it will have little resistance to sidewise movement, unless the PVC legs are fastened to the top. I would not put my display on something that anyone could knock over.
If you do build it or have the pieces cut then you should modify the design to provide more vertical support and more resistance to racking. 30" is a long span for either plywood or MDF. Two interior supports would be better, dividing the space into thirds.
Add a horizontal piece at least 4" inches high clear across the back. Glue and screw it to both the end pieces and the top. The braces both the top and the end pieces. If you go the L bracket route use 3 of the largest size that will fit (the screw holes get larger at the bracket size increases) to attach each vertical piece to the top.
