I have a Link Dac III also.
Was considering the upsampling also, but
found a person who does mods on dacs who
is very highly recommended. He will completely go through the circiutry and replace all the stock electronics with high
grade. His name is Dan Wright, you can contact him at themorgue.com , he charges
$250 for the complete job and he says that
it makes a much more improvement than the
upsampling. I'm going to send mine to him to have it done, will let you know how it turns out.