That new one may actually be a bit shorter than you might want. It all depends on the monitor you drop in it. Most arcade machines had a square opening for the monitor so it could handle either a vertical or horizontal screen by rotating it in the square.
However, most TV's are not square so if you're building this thing from scratch you have the advantage of making it perfectly fit any TV you decide to use in it. In that situation I would consider choosing your TV before deciding on final dimensions. Different TV's are wider, taller, etc.
Of course, if you use an arcade monitor, then none of this matters and a square will work just fine.