Question

I can't find any information beyond the 150 mW / 60 ohm load on the headphone outputs of the V2. This is a bit more than the Studio 68 which has an impedance working range of 32-300 ohms which would be fine for the 650's, but I don't know if the mW/ohm translates to the same range on the V2.

Answer 1

I opened a ticket with PreSonus support, as I had the same question (as an aside, I've had a great experience with their tech support every time I've had a question).  I was curious about what version of the Beyerdynamic DT880s to use with the unit. Here's what they said:

"Impedance usually provides a working range.  Typically you want to connect headphones and or speakers rated at a higher impedance than your connected output.  We would recommend using headphones rated 200 ohms or so."
 

When I asked specifically between which two models of the DT880s they would recommend, they said this:

"Either the 250 or the 600 should work well.  They are both very popular headphones used with our products.  You may need to crank up the volume more for the 600 ohms however.  

We'd recommend the 250s."