How many watts rms can i safely run on my 8 gauge amp kit?

i used to have a mtx terminator setup on my 8 gauge amp kit but i am now upgrading to 2 re srx 12' subs with 700 watts rms @ 4 ohms or i could bump it up to 1000w rms @ 1 ohm, however i dont know whether i need to upgrade to a 4 gauge amp it or not for safety and performance reasons