All those numbers are marketing gimmicks...in the real world they mean little.
Let me start off by asking you a question; what does a watt sound like? Even trickier; what does an ohm sound like?
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Speakers do not have 'watts'. A watt is a unit of measurement for work performed, much like horsepower. Do the tires on your truck have a horsepower rating? No, that'd be silly. Well, speakers having wattage ratings is quite silly in the same way. The thing that'll kill a speaker is heat (or an old/dull phillips bit). How do you rate how much heat a speaker can cope with? Well, all the manufacturers have their own system while others just slap whatever number they think will move more product.
With amplifiers, the best way to figure out how much work they can perform (watts) is by looking at the fuses on the case and doing some quick math. If an amp has 2x20A fuses on it (40A), the most work it can possibly do will be around 400w. Simply add a zero to the end and you get an idea. Why a zero? Well, more math; Voltage x Current = watts. Your amp will probably only see about 13v and since amplifiers are not perfectly efficient (get warm), you can round that down to 10. So 10v * 40A = 400 watts. Forget that CEA crap and the sticker on the box.
Impedance is basically a load the amplifier sees. Think of it as one of those treadmills where you can adjust the ramp angle. A brisk walk at 4mph is a breeze right? Now adjust the angle on the treadmill. Now you're breaking a sweat. You're not going any faster, you're just being asked to perform more work to keep you stationary and not fly off the back of the treadmill. The incline is a greater load just like 2ohm is a greater load than 4ohm.
2ohm is not better than 4ohm...I'd argue the opposite actually, but that's another discussion.
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You asked if the system is 'balanced'. Well...what does it sound like? Do you like it? If you do, it's balanced...it's really as simple as that. Do not get caught up in all the numbers & specs of 12v products as it almost never translates over to what you hear. Your ears will never lie to you, so let them make the final decision based on what they think instead of what you read on a message board or in product lit.
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Will your charging system handle the new system? Go back to those fuses on the amp. How many and how big are they? Remember I said to add them up and basically put a zero to find the amp's power capabilities? Divide that number in half...that's the max draw the amp will have when playing music playing at 100% volume. Do you listen to the radio that loud? Probably not as deaf people don't normally shop for audio equipment.
Your charging system & factory ground strap will be more than fine for your setup. You can spend the $100 or so on battery terminals, 1/0 gauge, rings, etc and I can almost guarantee you will not hear a difference. With good power wire of adequate gauge and a proper install, there will be no problem.
As far as wiring; RTFM. Your subwoofers should have come with a basic wiring diagram for various applications (1/2/3 woofers and their various impedance). Follow that and if your subs are DVC 4ohm woofers and you basically have 2 choices on how to wire them to the amp (4ohm or 1ohm) ALWAYS go with the higher impedance. You will not make 4x the power at 1ohm than you would at 4ohm. You'll just roast something inside the amp b/c that proverbial treadmill will kick it in the groin.
Remember I said heat kills speakers? It'll kill an amp too. Just like the incline on a treadmill will make you sweat, a lower impedance does the same thing to an amp. Push it too far and it lets out the smoke.
