Since this is your first time to the snow, i recommend you hire a board, around the 161 cm mark like your board calc says, buying a board can come later, you don't know what your riding style is yet.
Hehe thanks for the advice, reason that I want to buy my gear is because it costs quite a bit of money to rent in Australia, and i'm visiting my sister in the U.S.A. in june/july and with the price difference with the huge sales that are on over there at the moment (and possibly still while i'm there being your summer...then again it will probably all be sold and the 2010 seasons gear arriving?) i'm sure if I don't like what I buy I could sell it and probably come out even, and if I do then i've saved myself quite a bit of cash in the long run.
Also it might change once I get out on the snow, but the park doesn't really interest me, watching those guys barrel down the mountain on fresh powder looks sooo fun....but kinda scary too watching them start avalanches
With that in mind, the Rossignol One Mag comes in a 159 and then jumps to 163, I really like the look of the board and it has a few nice reviews and is a pretty good price at around $230. Would you suggest a the larger or smaller, or I guess more importantly is a 159 going to be too small for me freeriding and ploughing through pow?