I'm installing a 100w max Pioneer amp in my 96 Civic. Do I need to upgrade this wire? I'm upgrading the neg battery wire and engine ground wire to 4ga. If I do need to upgrade it, is it hard? Seems pretty cramped in there.

 

your probably dont "need" to espeically if you dont have any rough idle, dimming lights, etc problems with a tiny 100 max watt amp.. what is that? 25rms? 40rms?... but it should help since the wires may be old and corroded.. and supposing there are some resistance problems on OEM... if there is, this will help insure that your Alt is putting all the power it makes into the battery and not lost in resistance