I think it sounds good and compliments the stock speaker set up. It's designed as a "plug-and-play" set-up. The wires plug into the stock ones, well specifically they go/plug between the stock square plug and headunit, with all connections remaining intact.
The "hard part" is mounting it on the side, which entails removing much of the back to get access and running the wire down the right-side inner door sill trim.
Sounds worse than is, as only takes a few hours total.
The bass is enough to be too-much for me. There is a switch on the back for some adjustment as to it's timing (phasing, I think is the correct term). The volume/bass level control is next to the bottom hole. I tend to only run it at 1/4 level, which is enough to annoy my wife when she sits in the back (next to the youngest) right in front of the unit.
Plus, it looks pretty well integrated once installed!