My Aveo sports the Pioneer TS-D720c speakers matched to the AVH-P5900DVD. An awesome combo IMO.
I pulled the center dash off and checked under the areas for the crossovers. It seemed fairly clear. So, I brought out the Dremel tool and cut out a pair of holes to match the square shapes of the crossover. I made a base for it to rest on and epoxied the base to the underside of the dash. Then I made a metal jig to accurately drill the holes for the cables. Simple and effective I think.
Hacked a pair of metal flake blue Monster cables and routed them through a set of LED mounting rings.
The blue goes with the blue touches on the interior.