Clint: Like many, I looked for that perfect do it all lens. In the meantime I have also picked up some lenses that I would have never bought as part of a package deal, etc. I now have several 28-80's (Nikon and Sigmas) an 18-35 Nikon, an 80-200 2.8 Nikon, a 170-500 Sigma, a 70-300 Sigma, and a 28-200 Nikon.
I also have prime Nikon lenses at 50 (1.4) 85 (1.8) and 135 (DC 2.0)
Except for the 80-200 2.8 Nikon and 170-500 Sigma and the 18-35, it wouldn't bother me a bit if someone stole the rest of my zooms
Prime's always shoot better since they are purpose built around only one focal lenght. Zooms, generally represent a tradeoff in image quality in exchange for the convenience they offer.
I have never regretted buying a single fast prime lens. I have about six zooms I could do without.
The best zoom in the bunch is the 80-200 2.8 but it is a $900.00 lens.
If you can afford it, I would go with a nice 80-200 2.8.
If you can't, I would suggest either a fast 50 or 85 mm.
I can work around the loss of zoom range (well, unless I am at the zoo and just can't get any closer) but would trade zoom range for speed in low light over all else. I can think of few shots I missed because I couldn't zoom in or get closer, but I can think of 100 shots I missed because the shutter speed was too slow with available light.
Tamron makes a 28-300 that I have heard good things about, but I have never used it.
I can tell you if image sharpness is critical to your style, go with primes. I can look at my photos and in most cases tell you which lens was used to take the photo based upon how crisp it is. Prime's are crisp, zooms aren't, in comparison, unless you are talking high dollar glass, and most people looking for an all in one lens are trying to save some money.
The Nikon Silent waves are fantastic for zooms, but primes are still sharper at their respective distances.