I have a 1500 watt amp that i already had hooked up at 2 ohms. now i have another amp thats 3000 watts at 1 ohm. would it be fine to just use the same wire?
I depends on what size you original power and ground wire is to begin with. Assuming its big enough, yes, you can. IF not , the I would suggest not to use it.
But for all general purposes, if your not pushing it hard, it will be fine. But given you wattage, if your not pushing it that hard, why even have it ?