Re: grounding kit vs "big-3"
Useless. The only grounding I have are the Big 3 and I'm planning a common ground wire for my 2 amps running from the negative battery terminal to a ground distribution block in the trunk and split off to my 2 amps. From there, each amp grounded to the chassis in the trunk.
You don't even really need the common ground, I just did it for extra protection. Big 3 grounding and just grounding your amps to the chassis in the trunk would be fine.
'06 Civic Sedan
Second Skin deadened