I ended up ordering an arduino mega this weekend for $32 shipped of ebay. I was originally going to do the integrated chip route to expand if necessary, but since the mega has 54 digital i/o ports that's more than I could ever need and would be much easier to just use that than rig my own setup. I still might buy a new ethernet adapter though, the code for the ekitszone.com ethernet shield is pretty ugly and hard to use compared to the actual arduino shield library code.