(It seems weird to me: my sets and charger come in 4s, not 5s.) Other companies like Quantum make big external batteries that plug right into the SB800 while the SB600 has no such connection. In the old days we just rigged up our own connections to flashes, usually with wooden dowels...
For years I made do with three older strobes on PW's: SB800, SB900 and SB910. I very occasionally through in an old SB28 and SB24 for hairlights or background gels. On DSLR I used the very handy MiniTT5 and AC3 controller to wirelessly control the strobe power. I rarely, if ever...
Slow sync, Rear-curtain sync and Commander modes. The latter is used for wireless control of off-camera flash units. You can also attach an external flash to the Coolpix P7700’s standard hotshoe which is compatible with Nikon’s Speedlight models SB910, SB900, SB800, SB700, SB600, SB400...
are still not utiized... I KNOW, I've been schooled in this, that the on-board flash is not going to be sufficient, and yet I still have this resistance to sticking an external flash unit on top of my camera and/or another one on a lightstand to provide additional lighting... Sig...