What are the main benifits (if there are any) for using a down firing sub, vs the normal kind? I was specifically looking at Ascend's offerings.

If you have small children you can keep their little fingers out of trouble. If you have pets you can keep them from using the grill as a scratching post :). Seriously, if it is designed right, it does not make that much of a difference. More energy may be transmitted to the floor directly but that is it IMO. I had a down firing sub. It fired onto a wooden base. It was a ported sub. It sounded great. Now I have a sub with 2 15in drivers on either side of the box facing out. That sub sounds great also. It all depends on how the manufacturer designs the sub.