I am in love with my (large) Itti Bittis and my BumGenius BTP V3 - plus I have some newborn and small Sandy's waiting in the wings for the arrival of DS3 in February so I applaud your choices, ceb80.
From what I've read of the small and medium Itti Bittis, the advice seems to be skip the small and go straight for medium as babies soon fit in them as they are so trim.
Same with the Sandy's, really, the newborn ones are sooooooo minute (but cute as!). If you have a big baby s/he'd be out of them before you could say 'meconium' - and you might just want to wait til your baby has stopped pooing meconium before you start with washables? Maybe get half newborn Sandy's and half small which you can use more as night nappies to start with as a size up will be much more absorbent?
Like every other cloth nappy user, I love Airflow wraps, but for nights I much prefer fleece (Stacinators in particular).
Best advice? Start slowly. If you are like most of the posters here you will end up having tried at least one of every imaginable nappy and be well up on the pros and cons of each.