I've used 6SN7s with the 6922 adapters (from Tube Depot) on 3 different pieces of Decware equipment with terrific results. I'm a big fan of the 6SN7 and have an extensive stash, so it was definitely a win for me. If you search the Decware site there were many similar success stories.
Of course, checking with the manufacturer is always advised. I checked with Steve before I tried it and he thought the difference in the heater specs would be handled fine by his power supplies and he was correct. Other amps may not fare as well.
I thought the sonics were as good and often better than the 6922s I tried, plus I had lots of 6SN7s to roll. If you were starting from scratch and having to purchase either 6SN7s or 6922s, then the economic advantage pretty much goes away.