What size gauge power and ground wire would you use for this amp?

I have an Acura integra 2 door and I'm getting a mtx thunder 1501d(not the elite) amp. It's going to be in the trunk and I'm just going to run it at 4 ohms for now since I got a small sub. But I'm going to run it at 2 ohm later when I get my new sub, I'm only going to use one sub. So I was wondering what gauge size power and ground wire should i buy?and the wire has to be long as because its going to be in the trunk.