Hey Plummet,
It depends upon your budget. Of course if you want to maximize your light wind kiting, a dedicated light wind large kite and a dedicated light wind board will be unbeatable. Some combinations can get you out in under 10 knots on a twin tip to say nothing of the light wind capability of the Race boards and gear.
Most people have a reasonable "light wind" (~12m kite) as part of their daily quiver. Adding a 17-19m kite will cost around $2600 and will give you a few knots greater bottom end. These kites are quite specific in their duty. They are almost all park and ride kites relying on apparent wind to get you going.
A light wind specific board can be used with a 12m kite and will give you almost the same bottom end as the monster kite, but at somewhere between 35% and 50% of the cost of the big kite.
Adding a specific board and kite will get you out in a mere puff of a breeze, but it's gonna cost you some serious bucks. If you live in an area with a lot of light winds or a poor seasonal wind, the investment IMHO would be well worth it. On the WA coast, big kites are becoming more popular but they are still an extravagance. There are very few light wind boards over here as we have plenty of wind generally, but I think there would be a great benefit to owning a light wind board as opposed to buying a huge kite.
Just my thoughts as a rider. As a retailer, I suggest you all come in and buy big kite and light wind board combination .... in carbon of course!

DM