Hmm ( IN MY OPINION ) the JL sub is good but you will only need an eight ohm if you are running one twelve. ( from what I know you cant run a 4ohm by itself.. it has to do with running stereo, but I have never tried to run a 4ohm by itself, just have been told that and I have always ran 2 subs ) Now your saying you want to add a twelve and keep the existing 10 tube??? The twelve will be just fine by itself... You dont want to overpower the highs... thats cool if you stick under 400 watts you wont.. or you can get an epicenter so you can control the DB's of the Bass. AMPS>> I would not go with the Zapco because of the price... yea I do think they are the best amps in the world in my opinion.. but I pull enough power out of my Fosgate Punch 500a2 to beat my head in.. Running Mono 2ohm I am pulling between 700-800 true power into 2-12" punch HE's.. They are 400w rated and I have blown three... Thank god for the $16 anything goes wrong/blows warranty from Fosgate. Anyway the Amps that are designed to go with the deck are Kenwood Excelon.. You will be able to control the amp from your deck if you buy one of these amps.. ( Look on page 14 of your Kenwood instruction manuel.. UNDER Amp Control.. this lists the types of amps ) you may not be able to find them brand new ( dont know ) but you could prob pick one up on-line ( auction ) or maybe at a pawn shop. Unless you are dead set on the Zapco I would say for what you are doing you dont need that, and I would find a different amp. As far as running the RCA's the ones that are on the tube are ok for what you are doing ... You will need to run a power wire from your battery back to your amp and a seperate ground to the chassis.. With the watts under 400 ( true prob 200 or so ) you wont need another alternator and such because your draw wont be that hefty but over time (2-5 years) you possibly may have to replace the alternator due to wear ( no biggie ). Most decent shops will install all this for $1 to $100 depending on who you go to. If you dont know alot about installs, it will be worth the money and save you the hassle plus it will be clean ( at least I hope it will.. cant trust everyone ). If I didnt answer anything just let me know, or If you are confused let me know.. I can go on further.. Its 2am here and the screen is a blur, adios... Hope I helped... If I am wrong anywhere someone correct me please..C-YA, Ryan