definately put the kappas up front. as for an amp. i wouldnt either bother w/amping the rear. due to the God-awlful placement of the rear speakers. i would run them off the hu just for a lil rear fill. i'd get a jbl 80.2 and run it to the fronts. u can get it for about $90 shipped. i think the contour w/out an amp sounds best with the HU w/this configuration for the fader:
R.........l......X....F
the x is where i put the fader
a lot of contour owners just take the rear speakers out all together. a prefer a little rear fill but when i get some good componets up front i probably will forget the rear fill altogether. it just lessens your sq but since you have fairly decent speakers in the rear and your front stage will be much louder you should probably leave it balanced
just toy around with it, but i definately wouldnt get a 4 channel amp. even if the rear is loud, you wont hear much clarity or sq, its not worth the extra money IMO