. . . if you have never heard the difference that the C4S makes, I would most certainly recommend that you build the unit as originally designed first, and live with it for awhile, before upgrading. . .
The cost of the 2 or 4 resistors and the fact you learn from upgrading as JC says is the exact reason that Bottlehead doesn't custom pack kits with the upgrades. Doc has posted on this in the past but probably not on this forum.
Think about it. There would be kits including 4 resistors and no upgrade and kits without those four resistors and including the upgrade. Packing becomes more of a headache than it already is. There are precious few packing errors these days. Don't mess with success.