Primarist - I’ve had a Freya for the better part of a year now (and a Gungnir for longer than that). Have been very happy with both pieces. The Gungnir since the MB upgrade is spectacular.
First, on the heat: Compared to other tube gear I’ve had, the Freya with various 6SN7s does not get exceptionally warm. In fact, while I prefer JFET mode, when I do have tubes installed I’ve been a little surprised how relatively "cool" it operates. The 6SN7s don’t seem to throw heat like some other small tubes I’ve had in other gear. This is NOT to say the Freya surface right near the tubes doesn’t get hot BUT if you mean the whole chassis or areas well away from the actual tubes are "too hot to touch" - that definitely has NOT been my experience. I haven’t run Tungsols - maybe they operate differently? (seems unlikely), but have run new production EH, some NOS RCAs and NOS Russians (as well as the as-supplied Russian 6SN7s).
There’s a pretty active Freya thread over on HeadFi.org. See what the consensus is over there. I think Jason might actually participate from time to time. AND like mofimadness suggested, contact Schiit tech support (email is best). Like MoFi, as a general rule I avoid stacking powered-up gear. Heat kills. The Freya is on the top shelf of my equipment "console" with plenty of space all around. The Gungnir is on a lower but still open shelf. The Gungnir gets warm to the touch...a little warmer since the MB upgrade. But that’s all. Never hot.
I’m really happy with the Freya and consider it a step up from the 6H30/EZ80 tube preamp I used previously. I’ve used (am using) the Freya with a Merrill Audio Taranis Class D power amp as well as Hegel H200 operated as power amp in HT bypass mode.