I'd like to remove this thing to make more room for a custom subwoofer box I'm building to stick there, how hard would it be? Seems to be welded on there

 

Yep, it's definitely welded on so you would need to drill out the welds to remove it. The one really nice sub box I've seen that replaced the rear seats actually used those mounts to mount the sub box. That might be something to look into.

 

Hmph. I guess I'll just let the box rest on top of the hump. I'm patching together this new sub box out of an old trunk one, cutting out a groove to fit the hump would be difficult.

 

Itll look better properly formed to the contour of the floor