I'll contribute my experience: My system includes a pair of vintage bookshelf-sized two-way sealed speakers with 8" nominal diameter mid/woofers, about 83 dB efficiency and a maximum power rating of 200 Watts; driven by an AVA FET Valve 600R hybrid power amplifier rated 300 W/Ch at 8 ohms with appropriately rated speaker fuses. They are in a larger sized-family room, and played only up to medium-volume levels, when my wife is home. I am quite happy with them.
I considered replacing them at one time with some WOW1 speakers, but wasn't convinced that their mid/woofer diameter was sufficient for my listening situation. For near field listening, or in a smaller-sized room, I'm sure that the WOW1s would be a good choice.