I am not familiar with Clarion products, but I am sure the self powerd sub should have a crossover in there somewhere. So just take one set of preouts from the deck and if the self powered sub has inputs, plug em in.
As far as power to the amp for the sub, You should take a look at a power cable calculator. I think there is one on
An educated guess would be atleast 4 gauge wire for the positive side of the amp.
When it comes to the ground side, use the same or bigger gauge wire as you did for the positive.Make the ground wire as short as possible. Drill a hole and clean the paint from around the hole atleast a 1/2" all around the new hole. Use a good bolt and serrated washer to get the best ground as possible.
Put a fuse inline , within 18inches of the battery for safety reasons.
Now there should be a terminal on the amp called a remote turn on. On your Kenwood deck there should be a blue wire, maybe 2 of them or a blue wire with a white strip.
If there is only one blue wire on the deck it would be the power antennae turn on. Some of these can be wired to the remote turn on for the amp, but sometimes they cant cause they will only provide power to raise or lower the antennae.
Another blue or blue/white wire should be labelled remote turn on, wire that sucker directly to the amplifier section. You ready for bass.
Play with the crossover knob until you find a setting you like. Usually between 50Hz and 80Hz is good.
Try to run your power wires under the carpet near the door sills and your RCA cables atleast 8 inches away from them so as not to pickup any radiated noise from the power cabling.
Definatly strap the amp/sub combo down for those quick panic stops. Lotsa guys have big dents in thier heads from flying boxes.
Good luck