Need help on what solution to get for my D200.

I'm travelling to Africa next year, for a 10-14 day private custom made photo safari (wildlife). I'm not a rich man, actually quite poor, working for a well know environmental organization, and I have been saving for a couple of years now. Point is, no luxury solutions please, no matter what reasons.

I will be carrying with me my new D200 and a Nikkor 18-200 lens (damn waiting line ) as primary equipment. I will also be taking with me an ancient Nikon FE2 film camera as a backup (w Tokina 50-250).

I want a digital zoom range of at least 400mm. My primary choice atm is, after many hours of or reading reviews and forums, the Tokina 80-400, which has mixed reviews, mostly at forums, on it not being sharp at ALL at f5.6 to F8 or at 300-400mm. Others are saying it is quite sharp at these settings and has very good sharpness at all other ranges. The issue with this lens has been it's AF being very slow. The lens has gradually been getting better in both image quality and in AF. The latest one that got released just a couple of days ago has a completely new AF system and is now supposed to be very good.

-So, a solution giving me something in the range of 50-500 zoom, digital and under US$ 1000, preferable way under that sum.
-Pros and cons for the Tokina 80-400 ($650), Sigma 80-400($1000), Sigma 50-500 ($1000), or any other alternatives like a TC ring on a 300mm zoom or something (heard many saying this is never as good as having one larger singel zoom lens !! ? !).
I've also read that the Nikkor 80-400 ($1300) is not worth twice as much as the Tokina 80-400 and is not even better than Sigmas 80-400.

Of the two Sigmas, it seems as only the 80-400 has image stabilizing technology, resulting in the same prize as the 50-500 one.

-Is it really dumb to buy a big zoom lens without stabilizing technology for wildlife photography? Can't a bean bag compensate for this loss somewhat or is it an impossible task to take a 400mm shot, at sunset or sunrise, at a big cat chasing it's prey? without setting the ISO to above 400 preferably?


Thanks for any and all help on this!