Well I looked up the amp and did some research. The pic you have above is right, or you can do it a different way. The 300/4 can take a 2 channel input and apply it to all 4 channels for output. So with that you do not need the LOC from the HU to the 300/4 (front channel). You can do it the way you have it, but it is not needed. It will give you a small bit of control over your front channel by using your fader on the HU. That is all it will do for you.
The crossover you asked about is not needed with the amps you have.
The line output converters are the same thing as the JL speaker wire to RCA converters. Even if you bought the crossover you would still have to get the LOC or JL speaker wire converters. That will be the weak link in your whole system (but a needed item). You have bought some of the highest quality products out there. (that is my opion) Some people do not like JL Audio, because they are really high price. Most people feel you can get an equal or better amp for the same price. I have never had any JL equipment, because I will not pay the price they want for it. MAKE SURE YOU GET insurance to cover this stuff. Most standard insurance will not cover extra stereo equipment. You have to pay extra for the extended coverage. Go to your insurance company and talk to them. If you think you are covered MAKE SURE. I would hate for you to put all the time, effort, and money into this system for some ass to come and steal it.
The only thing I see missing is a remote turn on for the 300/4. The 250/1 has a signal sensing turn on, but the 300/4 does not. I assume your HU has a remote wire (most do). You will have to run a wire from the HU (remote) to the 300/4 to turn it on. I know the Eclipse CD players come with 2 different remote wires, one for the power ant, and the other for the amp when you are playing it in cd mode. If your HU does not come with a remote you will need to run a switchable remote wire to the 300/4. This will allow you to turn it on and off when you need to. The only reason I am saying this, it looks like your stereo is not made to run with amplifiers, so it might not have the remote. And seeing Eclipse CD players have the dual Remote wire config, your amp might only turn on when you are using the radio function of the HU. If this is the case you will still need to wire in a switchable remote wire. If you do not have the CD remote on the HU you could also run a wire from the fuse block that is ignition hot. (only on when the iginition is turned to on or aux) Let us know if there is anything else we can help with.
