Johnathon, I am presently using this complement of Sigma lenses, on my N80, D100, D300 with great satisfaction. They are the 15-30, 24-70, 50 macro. My newer long teles are the VR equipped 70-200 and the 150-500. All are excellent performers for my landscape and multi-stitched 'pano' image arrays in which I simulate large format images.
Each lens cost ~40% of their Nikon versions, a substantial savings for a retired serious non-pro. I also have my venerable Nikon primes (35,50,85, 55 macro) from the '60's for my F, still fully functional (as well as my S2 RF). I proudly bring this to your attention to remind you and a myriad of others that the most critically important tool needed in the photographic arts lies 'between' your ears--all the other 'stuff' are handtools.
Photographs that I created over the past decades, but more importantly in the last decade, the digital era, (Nikon or Sigma glass) are indistinguishable in their technical quality. Especially so when using our eyes (not a loupe) for viewing at the appropriate distance.
I have put away my NBS test charts several 'whiles' ago and now concentrate on the creating, not taking of fine photographs. Do not let anyone embarrass you about the pedigree of your gear--just show them your fine prints.
Bottom line: the Sigma EX lenses I chose will permit you fulfill your immediate needs. When your finances improve you can purchase the 'approved' glass--if you so desire.
good luck irv weiner