The Celestion G10 has finally arrived, after a month on order. Surprisingly, it says "Made in the UK" on the box. I was expecting China.
The K110 and G10 actually make a pretty good match. You wouldn't think so on paper -- the Celestion G10 is middy, low efficiency, paper dome, and often associated with a distorted Marshall sound. But the G10 adds colour and depth to the K110 in the mids and lower mids. The JBL still dominates because of the G10's comparative low efficiency, but that's fine because the amp still foregrounds the JBL, while the G10 warms it up, especially at low volume.
The amp is a 1990 solid-state Fender Princeton Chorus. No, it's not a tube amp, but it has the best Fender clean tone this side of a 12AX7.