Thats not a subwoofer, those are minute stereo speaker with an orifice mimicking a bass reflex system.
They are bound to sound like a dying mouse in any case, but the idea of 5.25 bay speakers has been around for a while.
For some it might have been the WAF on the table, maybe.
The input, well, silly far eastern accessory manufacturers were never above providing a simple bracket for externally looping the input, like a 3.5 mm plug in this case.
But many legacy sound cards before the whole SB live-era front panel craze had internal connectors for that purpose. Some in the form of simple dupont headers right behind the backpanel connectors.
Like some Aztech cards:
http://www.amoretro.de/wp-content/uploads/azt … r_pro_32-3d.jpg