David M wrote:I am wondering if I need a porter at all
I'd take a porter. Their local knowledge (weather, tracks, the best guest houses, etc) can be handy. I enjoy interacting with the locals and have some great memories from spending many many hours walking with them and learning about their lives and their country; much more rewarding than walking with westerners. Plus you have someone about if you get ill, have an accident, get stuck in bad weather...or get caught in an earthquake. Don't be fooled by the fact you can drive much of the circuit now and that there are plenty of tea houses, people die there all the time.
David M wrote: I would expect to carry about what I would normally carry for a day walk in the Australian bush in a small back pack

. It's the Himalaya! I don't want to be rude but there has been a recent trend of underestimating those hills and how bad things can go

. Remember you'll need a sleeping bag, emergency bivy and all those other survival things. My two duffle bags when I go over there always have a combined weight of thirty kilos (10kg of which is climbing gear) and I feel as though I have perfected what I need over there now.
Remember if you hire a porter you'll be helping them, their family and the general economy of Nepal all for a very, very small cost to you. They have had a hard time of it over there recently. Your call though.
Also, the porter will probably expect to keep the pack you provide so I'd pick up a cheapi in KTM or Pokhara and I can't see why a North Face rip off duffle wont do, should cost you about AU$20 over there.