Jeff & Wendy, Jack is right about the great price on the 600W unit from Xantrex. I paid $485 for my XS400 from Jamestown Distributors. The biggest difference that I can see is that the XS400 has an isolation transformer built-in to automatically override, or bypass, the inverter off when shore power is plugged in. With the 600W unit you might want to go with the Blue Seas AC Source selector switch, which is what I did for my new Whistler 800W mod-sine wave unit. As I recall, you are teachers and use your computers a lot, which makes a pure sine wave unit important.
I did a bench test on my Xantrex and it works fine, including the remote control switch.. Apparently, in my never ending quest to prove myself to be a slow learner, I didn't properly reset my GFCI outlets when I last tested them. I jumped to the conclusion that this was just another Xantrex unit (see my earlier posts about my XC500 charger) that crapped out on me and didn't discover my cleverness until after I had installed the Whistler! Duh . . . Anyway, I like the 800W output of the Whistler. It's a simple, cheap unit and I'll just have to see how long it performs. Tom Koehl