the only thing I find myself really missing is the high quality of the high iso (9000, 12800) shots I can get from my D700. Hence, I am looking for a film that I can reliably push to those kinds of speeds for darkroom printing.
First off, you probably won't get results you like at those ISOs with film. Maybe 1600-3200, but much above that is going to be dicey and VERY dependent on how you expose.
Second, if it's really for darkroom printing, what I say goes double. Most of the examples you see of this kind of thing have a) questionable metering and b) are scanned. You will probably have a tough time getting all the contrast and range from your paper that you might need for a severely underexposed neg, like Tri-X at 12,800. You can do a lot of extreme contrast changes after you've scanned that are more difficult or impossible to achieve in the darkroom.
But, by all means, try things out. I'm of the camp that if you want speed, you should use a fast film, T-Max or Delta 3200, and stick it in a speed enhancing developer, like XTOL 1:1, DD-X, or Microphen. I've gotten great results from T-Max 3200 at 3200 in XTOL 1:1, though they are usually better at 1600.
I played around with doing some stand tests at higher speeds in XTOL 1:3 as well. The negs were definitely more developed (tones were shifted up much higher), but I'm not sure if there was really any more detail in the shadows...