The Multibit Gungnir is USB5 and the Mjolnir is the first generation. I bought these for a secondary system for watching movies. I decided to upgrade my monitor in my main system so no longer need these. I am the second owner and haven't had any issues with either.
Asking $750 for the Gungnir.
Asking $350 for the Mjolnir.
$1000 for both. I will cover PayPal and shipping at my asking price.

My thoughts on the Mjolnir: Similar sound to the Asgard 2 but with more details and obviously more power. I used it to drive the HE6se and Abyss 1266TC with no problems. I think it paired well with my Stealth and the HE1000V2.