After reading Antares post, all I can add is: Do you already have circular needles? If not, you'll want to be sure you have one long enough. Interchangeable circs come in handy that way because they come with different length cables; some circs have cables you feel like you have to fight with because they coil or are less flexible. If you run into problems be sure to ask, someone will almost certainly be able to help.
I should never overestimate my basic arithmetic skills.