Non-New 3DS owners will have to wait a little while before they can make use of those amiibo on their old units.
http://www.nintendoworldreport.com/news/39418/3ds-nfc-adapter-coming-to-japan-this-summer
The Nintendo 3DS NFC Reader Writer adapter is scheduled to release this summer in Japan. While no specifics on price were given, the device will allow owners of original 3DS and 3DS XL units to use amiibo in 3DS games.
There is currently no word as to when the device will be released in the West.
