So, just for kicks I did the math on this since I'm driven crazy by the weirdest things. LOL
If this is a 10g tank, the sponge you have roughly covers 120 inches.
If 4 large double sponge filters covered the back wall, it would cover 129 inches because of the cylindrical shape and top/bottom areas as well.
One thing for sure. Yours looks less obtrusive!