update on alternator noise over speakers

[TM]

Huw, and anyone else knowledgeable on this topic-
Is wiring the ground to the negative battery terminal a bad idea?

I'm going to try to undertake my stereo install this weekend (I have
Monday off as well), but am a bit unclear about this part. The hacks
that did my last system grounded the amp to a bolt in the rear deck.

I plan on cheating a bit and using one of the pre-made amp wiring kits
if they work well. Something of decent quality, though- probably a
Fosgate or Streetwires kit.

Taka