your accessory/trigger wire does not need to be 10/12 ga-- 18 ga will work fine, and is typically recommended. it does not need to be fused, usually it is protected by a factory fuse, but it can help, and make it easier to trouble shoot-- like a safety net--one more won't hurt, it is just one other extra expense...
you do not need to run the ground wire all the way back to the battery-- it is typically recommended to use a short length of cable(typically 1-3ft) and connect it to the nearest ground point.
but again, if you do choose to run the ground to the battery, make sure to double the original gauge size to deal with the extra resistance in the cable.. again, just a extra expense that might not be needed, but can be done if you feel it is necessary.
could you provide a link to that sound ordinance sub? i can't really make out the model number--so just so i can make sure that everything for that falls in line as well
for the fm modulator-- not sure how much research you have done with them, but they are sometimes reported to have poor audio quality, while the audio quality is debatable--my wireless ipod fm modulator seems to work fine for me in terms of audio-- it emits sound , whenever i i use mine though, i always need to reprogram it for other stations in the area-- and that can change even in 20 miles-- but both of these factors can vary widely with the brand, and quality of the modulator you get..
if you can locate one that physically plugs into the radios antenna wire, it will provide much better audio, and reception quality then a cheap wireless version.
Thanks for the advice. You have answered two of my questions. I was not really sure if the accessory wires had to be fused or not. I also realize the 10/12 migh be a bit overkill there and will switch to 18 ga. Also I am still up in the air over whether run the ground wire back to the battery. I alt ground plan would is to use the groud dist block with the ground wire to one of the set belt bolts. I would obviousle clean the connection to clean steel.
The sound ordinance Bp8t (http://www.crutchfield.com/S-dNWdgeB...nce-B-8PT.html) from Crutchfield is cheap but gets good reviews. I dont need to rattle windows. I am replacing all of the factor speakers with Polks audio Db 651s speakers and just want to add a little more bass with the sub.
As for audio input I am using a Sosche universal audio input that is powered and wires directly in-line with the antenna.
Maybe you can answer two more questions for me. First I plan to run my V70-XB 7" screen off of the P4 adapter. I have read that others have done this and that it supplies clean 12v power. Secondly will the stock Ga of P4 connector wire handle the ppower requirments of the screen. Short-Circuit.com does not list power consumption but based on similar screend i cant imagine it uses more than 10 watts. Based on my research the sotck wire should be good.
if you can locate a factory ground point in the car, or a light-structural bolt, that would provide a better, more consistant ground point then a seat belt bolt-- seatbelt bolts can be hit-or-miss on grounding quality--there is also the structural/safety issue with using a seat, or seat belt bolts-- depending on how you wire the ground wire to the bolt, it could affect the rated load of the seat/seatbelt in the event of a crash...
personally, i would not get the ground dist. block, at first, and plan on just hooking it up to the nearest bolt-- if you end up with a ground loop, or other ground problems, then options like ground dist. blocks could be a possible solution..
its a "if it works, don't fix it" kind of thing--it can also help save a little money by not needing purchase larger amounts of power cable..
but if you do run it back to the battery, it wouldn't hurt to use 4ga wire instead--the problem with running wire long distances in a car is voltage drop-- for every amount of distance, there is a certain amount of voltage that is lost-- and trying to ground your equipment that way can put a little more strain on them (the electronics are sucking from 1 small line, and pushing back through another, if you will...).
for the sub-- let me know how it goes-- i got a family-truck that might get one if it goes on sale for cheap(it being a family car, i don't want to put too much money into it). and the 8ga wire going to that will be fine.
you might want to consider using 4ga for the wire from the battery to the distribution block-- just to make sure that there is enough overhead for the sub, and carpc(being that the carpc will need a 12-10ga wire..).
for the fm modulator-- it sounds like you have a decent one.
not sure on the car, but some cars, while they might have a harness for something like a sub, it might not be connected to anything in the car-- so you might need to connect the line-out converter to the rear speakers..
for the question about the screen--the description for it says that it comes with a ac adapter-- maybe you could contact short circuit, and find out what the ac adapter is rated at- that should give you a very clear idea of what the screen should require from your power supply.