well, you will get s*** from someone on here, i guarantee it......be prepared for arguments about spring rates, damaging this, damaging that, bouncing, blah blah blah...people seem to forget that that's the way it was done before adjustable coil-overs were made and you could order springs off...
they are all decent brands, i dont see why not. as long as you stay away from the off brand "HIGH POWER" crap out there you should be fine. if you're extremely anal about sound quality, dont mix brands, but for the most part you wont be able to tell a difference.
the KDC looks to be on the lower end, i would personally use the KVT. Im not a fan of anything sony, EXCEPT the old school amps they produced when they started getting into mobile audio. just by-pass the driver safety mode with a switch, wire in the amps and you'd be good. As far as the 8's just...
could always ditch the 6x9's and put the 8's on the rear deck, and put the 12 in the trunk....depends on your skill level and how far you want to go. it could end up sounding amazing if tuned correctly, or complete s*** if half assed....also not sure if you mentioned what head unit you are...
"input shaft speed sensor" mine did the same thing. it's like a $110+ part and takes 5 min to install. looking at the tranny from the top, its right there plane as day.
well by looking at your user name, im assuming you listen to some form of rock music. if that's the case then the 8's will be a better choice. i have a single 12 in my p5 and i listen to all forms of music, hip hop or anything with a deep beat sounds great but the 12 lacks the punch of a 10 or 8...