I had the Osprey for 5 yrs and wow what that amp produced and working with Dave Thomson through the years with tube upgrades was amazing in every upgrade on soundstage that it produced,,,
At end I had Power Tubes --Military 1970 6L6GC
Row 1 Siemens ECC81
Row 2 6060 Yellow T's
Row 3 Jan GE Black Box and you could try 6414 Tall's.
These are the tubes I am running in my Reflection except Power Tubes are KT88.
These tubes produce the purest sound and detail for Raven Audio Amps