Frenki_:
Do you think we could use this cheap Enc28j60 boards, which are on ebay for 4$ instead of using AS-DM9161?For connection to SAM3X8E ethernet pins I would go with pogo-pins mounted on the bottom of DIY shield for DUE.
The ENC28J60 is an SPI connected MAC/PHY chip. It would work, if you have a driver for it, but would be a lot slower than a PHY connected to the ETH interface on the SAM3X. If you are doing occasional requests like HTTP, it would probably be OK, if you want to transfer a lot of data I think it would be lacking performance.
It is a cheap and relatively simple way to add Ethernet though.