The 900 is nice in quite a few ways. The 200mm zoom is very cool and the focus light works a lot better with the 51 point AF systems in the D300/700 and D3/x cameras. It's also more powerful etc etc. The convenience of the 'remote' / 'master' switch may or may not be a benefit - I never use on camera flash so my SB-800s are all permanently on Remote anyway.
I'm looking for a couple of extra lights as well but I'm hanging on for the SB-700 (or whatever it will be called) as I'm in no rush at all.
It's hard to say really. If you factor in future re-sale value then it probably is worth the extra. If you are just after a couple of drone flashes to add to the output, there are cheaper ways of doing it than either of the Nikons mentioned.
Is the CLS important or do you set them up in manual mode?
Thinking in terms of manual flash's, something like the sunpak 333, or the vivitar 285 may fit your needs. I dont know the specific's of the vivitar, though as i recall the 333 has a GN of around 90, 3 automatic modes depending on flash/subject distance, and full manual mode with power settings from full to 1/8th. It also has a built in slot in the flash head for gel's. 422 and 433 sunpak's are similar.
If you're using them primarily indoors, optical triggers are effecient and much cheaper than pocket wizards. Though you will need a camera mounted, or cable connected flash to trigger them.
If you do end up with some brand of aftermarket flash, and foresee the eventuality of using them on camera, be sure to check the trigger voltage. I believe nikon caps the save trigger voltage at 250, though i'd be hesitant to use a flash on camera with a trigger voltage that high. My old sunpack 333, and SB-800 both trigger at a nominal 6 volts and so far i've had no flash trigger voltage issues.
____________________________________________________________________ When no one is looking, Pigs can walk on they're hind legs
I am assuming you will be using the cheap remotes in a studio or on location where you will be the only one using flash. If so a Wein Peanut optical slave is the cheapest answer to your problem. If others will be using flash as well, the RF triggers are the way to go. Paul Buff manufactures the CyberSync line of RF triggers. They are reasonably priced and reliable. here is a link to one of his sites: www.alienbees.com. Good Luck and Enjoy your Nikons!