I am currently shooting with a Nikon D90 and use the kit 18-105 lens and a 50mm f/1.8. Mostly I shoot as a hobby but lately I've been asked to do some family and engagement shoots. The 50mm is lovely, great depth of field, great sharpness, great price! The 18-105 is not nearly as good. I'm thinking of upgrading. I know the Nikkor 24-70 f/2.8 is great and I've also read a bit about the Nikkor 17-55 f/2.8. Both lenses are quite expensive though (I'm in Canada so add a couple hundred dollars to any american prices).
Any suggestions on other lenses that might do the job? I'm open to Sigma/Tamron if they have great lenses, but so far I've stuck with Nikon gear only. I'd like to have some zoom range (so prime and fixed lenses probably won't do the trick - although a nice macro lens does seem to be good for portraiture...). I'm open to buying used, but I'm located in Newfoundland Canada so the available used lens market here is pretty small and I'm not sure about buying from eBay for a lens... But I could be. Any and all suggestions welcome.