Personally, i would never run 1500 rms to a level 3, only people that are too proud of such a brand could do such a thing but it would definately handle 1000 daily.
If you ask me, using two 8 awg wires are fine, i did that for a while and nothing happened, but for a permanent install its best to wait for your 4 awg wire. After all, all you are doing is just doubling the ammount of copper.