Hi Carl,
Great to hear you are planning to spend some time in Brisbane before heading up north. I think the important thing to keep in mind is that Brisbane is a great base from which to see South East Queensland.
Not that I want to make Brisbane sound boring, but you'd probably go crazy if you spent a full week in Brisbane. It's not that much of a tourist hot spot. You could probably see most of what you want to see in Brisbane in two maybe three days, depending on how much you like art galleries and museums and the like. Of course if you have a mind to it there's also the islands South and North Stradbroke, which you could easily spend a few days visiting.
What I'd be planning if I were you, would be to see some of the areas close by to Brisbane. The Springbrook area in the Gold Coast hinterland is not to be missed. A day's drive out to the Darling Downs immediately west of Brisbane will also give you a view of the coast and an idea of where Brisbane lies in relation to the rest of the country.
Then there's the Coast north of Brisbane. The Sunshine Coast is not so full of high rise as the Gold Coast and depending on what takes your fancy you might find it's a better place to kick back and relax. There's lots of suggestions of things to do on the website
http://www.new2brisbane.com.au/Explore.html.
Or post back here and I can be more specific.