Matt Laur 
, Mar 24, 2009; 10:02 a.m.
Most people who have 800s and 900s aren't going to be parting with them willingly, and you always want to think twice about used strobe anyway (you have no idea how much it's been cooked by aggressive use, and there's no way to easily test if the tube or capacitors are five minutes away from being roasted).
The usual places (try the Adorama search at the top of this screen), Amazon, B&H, etc., are going to be very competitive with one another on factory fresh stuff. It would sure be nice if the 800 (if you can find one!) and the 900 were less expensive, but they're simply not. The 600 - if you're going to use it on camera, or as a slave to the D80's pop-up, is quite effective - especially relative to the 800, for the money - but does cut some real corners for certain kinds of use (like being a simple optical slave to other non-Nikon sources, or when you want to easily cable it up to a PC cord/radio trigger, etc). But if you need an iTTL/CLS speedlight, now, and your budget is as you say... the SB-600 may be your best bet for the time being.
