I'll be going to South Africa in Nov-Dec and will be spending a few days on a safari in Kruger, and I need a lens with some more reach (Nikon mount). The 70-200vr is just not going to be long enough, even with a tc if I were to pick up a 1.7x. I've narrowed it down to the Sigma 50-500 (Bigma) and the Sigma 150-500 (Bigmos). I'm not considering the 80-400 nikon because I'm not impressed with the optics, the focus is slow, it's due to be replaced, and it's $1600. Has anybody had any experience with either of these two lenses? I'll likely be using a monopod or a bean bag for stabilization, so image stabilization (OS on the 150-500) isn't a necessity, but I'm curious to hear from people who have used it if it is effective. I'll also be buying a Canon 100-400L for my fiancee, for whatever it's worth.