I bought a new 23 GX Luxury in late November and am wanting to get some ideas on what other's have done to be able to carry snowboards, up to 4 or more.
I have stock roof rails but don't have any cross bars.
First, do you have cross bars for your racks?
If so a good suggestion is a Yakima or similar roof top box. You can stow snow boards along with the snowy/muddy boots and other gear when traveling.
They're safe from prying eyes and the elements when traveling. It opens up a lot of room inside your GX from the stuff you don't need in the cab when driving. We had one for a while and it was nice.
NOTE: If you get one ALWAYS be aware of parking garage entrance heights!!!! Made that mistake only once. You're roof height isn't 73.8 inches any more.
I use a Buzzrack hitch mounted carrier, which works well for us. Quite a bit cheaper than similar carriers from Yakima etc, at the time I was shopping, but I've used it for 3 or 4 seasons and I'm happy with the quality.