power wire ?

[b-dubs89]

i have been thinking about my next project and the thought of running 1 or 0 gauge has occurred to me , but i am not sure if it is necessary or worth doing for this build . i am looking at 3 rf 10" p2's a 15" t1 and will be running 2 mono blocks rated 500 watts rms @ 2 ohms for now and in the future replacing 1 of them with a mono block in the 1000 ish watt rms range and a couple smaller amps for mids and highs . don't plan on upgrading my alternator as of now but i may change my mind in the future on that one . when is 4 gauge no longer sufficient ?thanks in advance for any answers