Keep in mind some of those units might not be as sturdy without the backs on them.
I checked the assembly instructions and the backs are nothing more than colored particle board held onto the sides with finishing nails so not much strength being provided.
I know that you did not go with one of the shelf units with fireplace, but I am just now seeing this and wanted to add some comments for anyone considering the same.
The back panel does not need to be made of solid wood or plywood to add substantial strength.
The back panel prevents the unit from collapsing by providing "cross bracing"!
From an intuitive standpoint, I think this image helps:
If you got rid of the two braces (making an "X") in the back, I think it is reasonably obvious that these shelves would be pretty weak if you were to grab the top and push it from side to side!
The console/shelf unit you were considering is not near so precarious as the one in the above image, and the firebox should be very sturdy to provide adequate support! However, since we are talking fire, the consequences of a collapse are too dangerous to casually remove the back without more investigation into it's strength (say a 250 lb person fell sideways into the top panel)! You could probably get away with using something like a 2" hole saw to "pepper" the back with holes for cables and ventilation as long as you left around 2" between all holes. However, if you are going to invest the labor to layout and drill the holes, go ahead and replace the back with 1/4" plywood which will be stronger after the holes than the particle board was before the holes. (since this is a safety concern, I am inclined to be overly cautions).