Welcome to Nikonians! And it looks you've done your homework well! I commend you for considering the tripod right off the bat, all too many folks forget about it, or start with some shaky $30 tripod and then wonder why the images are not sharp. Especially since your priorities are landscapes and macro, and you want to print big (from those D800 files!), the tripod should be next in line after the D800.
So, as to the tripod: The Gitzo model you picked out is excellent. I had a similar one (until I "upgraded" to the RRS model). The only thing you might reconsider is 3 sections vs. 4. The 4 section model you picked out will collapse to a smaller package for traveling etc. but it is a bit less stable than a 3 section model, and more importantly, you will be spending extra time to extend and collapse those extra section every single time you set this tripod up. It was enough of an annoyance for me to go to a 3 section model. So it will depend on your priorities: a lot of airline travel (4 section) or a lot of walking around / setting up / moving on (3 sections).
Beyond the tripod (and bullhead), there won't be much money left over in your budget. But that camera and tripod should last you a long time. For the macro lens, you can get very good quality even with a fairly inexpensive model. Practically all macro lenses are very sharp. I.e. check out the Tamron 90mm f/2.8 which has gotten very good reviews, and Thom Hogan says it's optics are on par with the Nikon 105mm f/2.8. Personally, I use the Nikon 200mm f/4, and this is the best macro on the planet if you ask me (and I tried many including Zeiss), but that may be beyond the budget. The advantage of a long macro lens is the extra working distance if you're into insects and such. If the Nikon is too rich, then the Sigma 150/2.8 that you are considering is very close at 2/3 of the price.
For landscapes, the 14-24 would not be my first choice. Yes it is optically excellent, but I found 14mm to be rather impractical for landscapes, while 24mm is often not long enough. My landscapes are mostly between 20mm and 35mm. That is subjective, though, some folks like the ultra wide angle. Another point against the 14-24 is that it is very impractical to use filters, that only works with an external contraption. I use Zeiss prime lenses for landscapes, but if your budget is used up by the tripod and macro lens, here is a "secret" tip: The Nikon 28mm f/3.5 AI lens is excellent for landscapes. I got mine for $50 at KEH (used) and it rivals many lenses that cost 10 or 20 times as much. As a side benefit, this lens is extraordinarily resistant against flare (beating the 14-24 by a big margin), so you can shoot even directly into the sun without ill effects. And stopped down it is sharp across the frame. Noted landscaper Bjorn Rorslett writes about it:
"The 28/3.5 performs excellently on the newer D2X and D200 digital bodies, giving very sharp and crisp images with just ever so slight trace of CA. Shooting into directly into the sun with this lens is a breeze. This lens is one I nearly always carry with me on field trips."