I have a Gungnir multibit which was a experiment for a friend who we decided on a Yggdrasil. I think it depends on your long termed intent. If it is to build a much better system over time then I would wait until you can afford to buy a Yggdrasil. If you are thinking this is your final destination, I would do the upgrade. I was a long time skeptic of Schiit… but their performance makes up for their ineptitude in marketing.