Setup advice Silverado

[Scottwynns85 0]

Hello all I have a 2015 Silverado crew cab and I finally have the funding to play a little 

my goal is to have a 5k amp and 2 15s subs in ported box, the whole back cab will be sacrificed.    I need to know if a 250a alt and a good batt would be sufficient for what I’m looking for or maybe that and an extra batt? 
Also I keep reading about this donut deal on my negative battery cable that regulates alt voltage, and that it’s a pain to get around?   I haven’t dug too deep into it, but i wanted to start with at least a big 3.     Any help would be appreciated.     Thanks