It's hard to tell.
The L out on the back of the speaker doesn't look like a normal terminal.
If it's line level then you could tap the sub out there if it turns out that the subwoofer output is on the left side of the input jack. It it wasn't then the sub would output inside the cabinet and center would go to the subwoofer. You would reverse the connections somewhere in the signal chain in that case.
If it's speaker level then it makes more sense to just split the subwoofer signal off the PC and send it to the 2.1 directly. You would have to use a speaker to line level converter to drop it down again. Won't sound as good since you are going through raising the signal and then dropping it back again for no reason.
You won't get left and right fronts through the 2.1 only bass. Hook an amp to the front outs and connect the Daytons to it.