The K-1000 was designed to be driven by speaker amps. I have very little experience with the WA22, so I won't comment.
But since the K-1000 can use a much wider array of amps, broaden your search.
Personally, I'm not a huge fan of going balanced. It often increases price dramatically and the benefits are arguable.
What I really enjoy with my K-1000 are DHT (directly heated triode) amps. My K-1000 has never sounded better than when run off 2A3 tubes. I run my pair from the speaker taps on the Moth Si2A3. Pure magic. I've also run them off an Audio Note 2A3 amp at a meet. Didn't get a lot of listening in, but it was sweet.
I'd look into the various 2A3 amps listed at Audiogon. Include other DHTs, like the 45 and the much-loved 300B. While not balanced, there's every chance you'll be floored by how good the synergy is with a K-1000.