In my experience a 45-50W amp + 90-92dB speakers is a sweet spot if you are looking for a seriously good sound for sane money.
My current LTA Z40 is about 48W at 6 Ohm, its' volume control goes from 0 to100, and I mostly listen at 4 to 6. The speakers are 91dB.
I could probably use a 10W amp, but a bit of a headroom never goes amiss. And the tubes are never stretched.