I haven't powered them on yet, but I got a few net6501 from soekris that I think will do what you want. It's not speced to run amd64 mode, but people say it works fine. I am using a net5501 (which has 4 100 Mb/s interfaces) as a router with no issues (netbsd-5, i386), after disabling the crypto coprocessor kernel options. Why do you want to run amd64 instead of i386 mode?
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