The 200-400 reach isn't much difference than the 120-340 I get with the 70-200 with 1.7 but I also lost a stop with my setup as the best it can get is f4.8. That extra stop would have been really helpful as we seemed to see the most on evening game drives when the light was pretty low. I left the TC on the 70-200 the whole time, but I had a D40 with an 18-200 next to me just in case I needed a wider shot. 80% of my pics (3300 or so) were with the D90/70-200/1.7 setup. I took another 700 on the D40 with the wider angle. If I had time for sunsets, panos, and whatnot, I put the 18-200 on the D90 just for the quality and iso performance bump.
Because I am a US expat in the Middle East, I did not have reasonable rental options, so I went with a setup I can actually afford. I already had the 70-200 and D90 for sports like high school football and basketball and bought the 1.7x tele as a refurb for about $300 with plans to someday go to Africa. I knew I would never be able to justify $5000 for glass as an amateur photographer. If I was going to from the the states, I would have rented an FX camera and the 200-400 or maybe even the 300 2.8 with a TC. It would have cost me close a $1000 I guess for the rentals, but better than the 10K the setup would have cost.
The safari as a whole was great, I am working on building a website with a day-by-day blog and pics and will post it here when it is finished. I think if I do it again, which I may next summer, I may go somewhere not as restrictive. In Kenya they are very strict about not leaving paths to follow animals and you are not supposed to get within 20 meters. We were much closer many times and the animals did not seem to mind. You are allowed to leave the path for the big 5 but the game wardens in Masai Mara kept a pretty keen eye about getting too close or following. One morning we came upon a pride of lions with cubs, but I couldn't get a shot of the cubs because the grass was too high. The game wardens in a truck watched us for over an hour to make sure we didn't drive out to get closer.
i may try South Africa or Botswana next year on a more rugged trip that involves camps (Kenya was all nice lodges with 4 course meals) and following the animals on hunts. That might make for some much better photo ops and more excitement. A safari was the #1 thing on my bucket list (I am only 29) so I did get to mark that off at least.