DaveyJ - It has seemed like you and I agreed a while back the D300 was usable to about iso 750-800ish and for anything good, neither of us wanted to shoot above it. I actually thought the D7000 files at 1100 were the same as the D300 at 750 as well. That is my base line.
I would say the D800 for me is around 2000-2800, but at that level it is much better than the D300 at 800 and maybe even lower. The D300 at 1600 looks like the D800 at 6400-kind of. The D800's files are just so different with the amount of detail and color with the amount of noise reduction you can safely apply that it is hard to find the words do describe the difference. If you are cropping wildlife photos up to 30-50%, iso 1600 will give you gallery prints for sure. From 1600-2500 with no crop, you could easily keep a gallery print with a bit of PP work. Above 2500, it depends on the dynamic range and light on details - Low DR with light on the details, it is easily good to 3200 for an 8x10. High DR with little light on the details (i.e. back lit) it will look good on a webpage but probably not printed larger than a 5x7.
I'm really not a good judge on video at all nor do I have a base to go off of.
I have posted a few photos on my flickr account (just click my name and it is in my profile - and the d800 set) that has a bunch of high iso photos. It is kind of hard to tell what aspects of the photos that draw you to a yeah or nay conclusion. I'm kind of afraid you set the bar so high only a D4 will suffice. IMO the D800 blows the doors off of any DX camera released to date in all categories.
What I do know is that I shot a bunch of iso 400 film and I would take the D800 at 3200 over that any day.
As for lenses, the 70-300vr works better. I'm not kidding, it focuses and locks super fast now as do any slow lenses. my tokina 12-24 in FX mode can be used at 18mm on up, and the 35mm 1.8 works as well. Personally I would off load everything else and get the 24-85VR if you are looking to save some money. That lens sounds like it is built for video more so than any other. You probably will want something in that range I'm guessing.
What else can help?