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

For your 8 ohm speakers efficiency=sensitivity. Driven by 1W they will deliver 86dB sound level.  30W (30:1 ratio) should give you about 15dB more resulting in 101dB.   It should cover even symphony orchestra (EU directive limits level to 85dB in order to protect musicians).

Efficiency is defined as loudness at 1W power at 1m distance in open space.  Since average room is not an open space (sound is amplified by reflections) it can be assumed to be the same in whole room (unless room is very large).

YES! Doubling the power to 60wpc will only give you 3db more headroom. And if you want an increase of 10db (twice as loud) you will need 300 watts!

No.

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.