What I understand about headroom is, the difference between the power an amp can produce and the power asked from the amp. The extra power amp has is "headroom" and more the headroom, better it is.
Since your speakers are very efficient you'll probably be using less than 1W most of the time. With 1W you're going to hear 99 dB SPL one metre away from the speakers. 99 dB is crazily loud. Regular listening is more like 85 dB, so you won't be using up even 1Watt! 29 Watts will be your overhead.