I remember the threads about the HB cabinet and seems like the DSL isn't that old, right? The speakers might not be broken in yet. FWIW, V30s (the "v-type" is a budget V30) do have a lot of midrange 'honk", so it very well could be the speakers. I haven't used V30s in a long time just for that reason, although been thinking about trying them again because my tastes have changed some.
And house levels really don't open the output tubes up, you're probably only running at 3 - 5 watts.
6CA7s were great tubes, not really familiar with current runs and NOS ones like in JMP/HBE's pic will probably cost 1/2 as much as you paid for the amp. Like anything, get some current ones, it's always worth a shot, and if you don't notice much difference, you have a backup set of tubes. Don't rule out different speakers too, maybe find a decently used speaker to try.