I'm not sure about 2nd gen but there's not a lot of room under the seat of my first gen. I mounted an amp under the passenger seat, and it barely fit, after a little grinding on the top of the amp. To mount it I removed the seat, made 4 small holes in the carpet, and just ran screws with big washers up from under the carpet. It doesn't move around at all and I'm not worried about it ripping the carpet or flopping around. To make sure it fits, just slide it under the seat and move the seat all the way forward and back, your amp looks smaller than the one I used so you should be good to go.
As far as grounding points, any good metal surface will work. You could run the ground through a big eyelet connector and sandwich it between the seat frame and the floor, the seat bolt will hold it. Make sure you sand/scratch the paint off the body and bottom of seat frame so the ground has a good connection.