Hey Bruizer. INterestingly, this thread comes up about 82 times a year and it always amazes me to hear the answers that get posted. Mate, you like th elook of Bredli so get one fo them unless it is out of your price range. I know peoplke that own all of th especies that you have mentioned above and have also been recommend due to them being placid. All I can say is that there are ballistic snakes of every species that has been recommended above. I once read an article on Reptiels Australia Magazine that rated all the common pythons in terms of nature, feeding, housing etc. The Murray Darling was the winner. That said, I have two Murray Darlings (well sorta) from the person who wrote the article. Although the article said that they are placid these things are crazy and bite me all the time. They are approaching 5 feet in length and still aren't letting up. People who own one or two snakes of a particular species probably aren't that qualified to talk about the general nature fo that species. Just like a person who owns a Pit Bull that doesn't bite.
So, from my personal point of view. Research the snakes that you like the look of and that fit into your budget. If they are too big for your house then that is also something you need to consider but basically any morelia (carpet) species can be housed in a 1200x1200x600 enclosure as an adult.
Oh, and just one thing for Diamonds that may sway your decision. They are native to Sydney and best kept (from about two years of age) in an aviary outside. And the aviary need not be that big.
And also, find out about the Hawkesbury Herp Society and go along to their next meeting. I know of at least one Bredli breeder who should be there. Talk to those people.
And good luck with whatever you choose.