I use a 32 watt for cloning in a three foot long, 18" deep, two foot tall box used just for cloning and that's barely enough in my book. I would step it up by let's say at least 150 watts.
I'm a out door grower also but try to clone most my plants to eliminate dealing with males. I have a small setup that consists of two 150 watt hps just to get me through the winter and it serves it purpose. good luck.:thumbsup: