Yep, crossovers under the passenger seat. The db6501's come with a selectable level boost (-3db, 0db, +3db) and I wanted to be able to access them easily. There was a bit of extra wire, but it really wasn't that bad. I don't have pics right now, but would be happy to take some tomorrow.
I ran the wires underneath the step pad of the passenger side of the car, and behind the 'T' plastic piece near the seatbelt. There was a tiny plastic piece that was held in with clips that I opened, pulled the wires through, and closed the piece again, sliding the wires under the gap between the carpet and the bottom of the plastic piece. I then wired the crossovers, put them in the box, and viola! No wires, and I have direct access to them.
The only problem I ran into was attempting to keep my speaker wires and RCA cables away from the power cable going to the amp on that same side. It wasn't difficult, though. Just a couple wire ties.