Amps and batteries?

[Mobileaudio25]

I'm running 3 agm batts (one under hood, 2 in the trunk). I'm doing a positive run from the under hood battery to the 2 in the rear. My box is pretty large and I don't have enough room to mount two batteries side by side so I will have to put one on each side of the box. I'm gonna have to ground each battery at a different location in the trunk.

1) should I power both amplifiers from the same battery? The one at the end of the chain?

2) should I ground my amps to the battery or ind separate grounds for the amps?

Thanks for the input, kyle