Class A 30 Watt Amps: Are they enough to drive my book shelfs?

No to "are they enough power for inefficient speakers?".

Yes to "is this a bad move?".

Used KEFs still get a good price, unless you absolutely love them, I would sell them, get a pair of efficient speakers (no ports), and plan on adding a small self powered sub for a bit more fullness. Not too much extra bass, just enough that you notice when you turn it off.

Efficient speakers set you up to try 30 watt tube amps, and very efficient speakers allow even lower power, and, self-powered subs take the bass load off the lower powered amps.

No.

tubes, transistors, transformers, capacitors, ... are all relative to the rated amount of power within certain specs. All are sized to achieve a price point. Other components are designed to deal with ... heat. If an amp truly could produce more power within specs, certainly the manufacturer would publish that capacity. It ain't so. Measured distortion prevents a larger rating.

reserve power not only for instantaneous bursts, move a low efficiency woofer forward, of low and enough power to control the woofer, and, have enough reserve to make repeated instantaneous bursts. Many subs have servo control to assist with the tight control to avoid distortion.

volume controls, preamp components, pushed to high output is not sensible to me. A lifetime of too much heat from high output is also not sensible to me. pushing tubes hard, why?

Play Mickey Hart,, even at mid volume, serious amounts of power is repeatedly needed, serious amounts of control of the woofer is repeatedly needed.