Definitely go with Sussex over EE, if you go by my experience. My two SS are laying fairly well now that the group of 13 is laying about 3 a day (no added light) but my 5 EE are giving me one or two a WEEK at best. They started late and have never laid more than 3 a week at their best. Mine are also flighty like a leghorn, and my SS run up to me to be petted. You should get some broodies either from the Australorp or SS; I have had at least one of each breed, and they are supposed to be inclined to go broody.
I don't have an incubator, don't want one. My broodies hatch my eggs. There have been some disasters but I also have several mutts of laying age from letting them hatch, and would probably have more but I took the eggs -- too many chickens right now. Chicks raised by broodies are healthier and wiser, mature faster, and there's no hassle of brooding them, lights, etc. -- mamas do all the work. I will NEVER brood in my house again at any rate -- that was awful.