If you haven't bought a regulator yet, now is the time to plan carefully; You could get a dual-primary regulator and serve your 2 sixtels at the same pressure off one side while force-carbing a corny with the other or; If you can spend the cash for an 'ideal' setup; A single primary regulator and 3 secondary regulators.
Tell us a bit more about what you already have and maybe how much you're looking at spending.
Oh, warning: Most of us will be highly recommending that you go with EVABarrier tubing and duotights for your keezer, so please talk to us in more detail
before you spend your cash.