Have a look at the Samsung models. I have had one (ML-3710ND) for a couple of years now, auto-duplex, ethernet and able to take high yield toner. I do quite a lot of booklet printing but for long runs take a pdf to a printers, who can fold, staple, etc. Have found it to be competitively priced to run, especially as I got a special offer recently for the toner (2 for one). Got mine from Printerbase.
How secure is your Wi-Fi?