Chip prices are pretty much irrelevant to my situation, because I don't have the ability to use the Wiznet chip: I could design a board for it, but I couldn't assemble it. The board in that instructable is doable, though.
That "rumored ethernet+Arduino" might, indeed, be a solution. If it ever arrives. Meanwhile, I just found this little critter, which is very close to what I'd build, myself (except for using the dual-row headers: I prefer single-row for ease of use with stripboards and breadboards). It's kinda like a "Baby Netburner", with an ATMega128 on it. It's intended to be programmed with AVR Studio, but it's got a JTAG connector, so I'm a-thinkin' it should be possible to put an Arduino bootloader on it.