You could always try both ways and see if one sounds better than the other. As Jerry states above it's usually best to use your better volume control for controlling volume.
Both preamp and power amp have volume controls. Preferred method to control volume levels?
My power amp (Whammerdyne DGA-1, 2A3 tube-based) has a volume control (passive) as well as my tubed preamp (active). I’ve been running the amp with volume control all the way open and controlling the volume level with the preamp. However, I could instead run the volume control on my preamp full open and control the volume level with the amp. Does one way or the other cause more strain on the power amp tubes to achieve matching volume levels (SPLs)?