the bigger the better, anything over 600wrms i try to use atleast 2ga and anything over 1200wrms i'd try to use atleast 1ga. will 1/0 even fit in the 1000/1.
no, 1/0 won't fit in a 1000/1, so you'll have to reduce it down to fit in the amp.
with wire, you really can't over do it. the bigger the better. also, if you go ahead and get a larger then needed wire now, you won't have to buy new larger wire later on if you decide to upgrade.