>One other low cost option might be to buy 1 SB-700, 1 SB-600 >and 1 SB-400 if money is a big issue. The SB-400 is not as >powerful as the SB-600, but it really depends on what types of >photography you want to pursue.
The SB-400 is a nice little CLS flash, but, unfortunately, it cannot work wirelessly. The term 'CLS' does not mean wireless. CLS is the overall flash system, characterized by the way it fires a Monitor preflash to do its metering. The SB-400 fires a Monitor preflash to do its metering, but it will only work in the hot shoe. Also, it does not have a Commander mode, so it cannot control CLS wireless flashes.
>If you're experience with off-camera flash, you could look at >non-Nikon flash units, but using CLS might not be possible.
Watch out! Mixing CLS wireless flashes with non-CLS wireless flashes is nearly impossible. The problem is that the CLS Monitor Preflash will trigger all non-CLS flashes before the shutter opens.