also depends on other ratings for the speaker, like sensitivity. Generally, I stay away from amps that don't have listed power specs into 6 and/or 4 ohms. The power doesn't have to double, but when the power rating at least increases, that is a sign of a good amp design.
It's not that your 4 ohm speaker would sound bad with the 15.2, it just won't open up to its full potential without good amplification.
I really haven't researched truly efficient, high ohm speakers because I have heard several of them at RMAF over the years and did not like them. The sound I prefer (in my price range) is Monitor Audio, B&W, Dynaudio and Quad's L-series, and these are not easily driven. Hopefully someone here can suggest efficient speakers.
It's not that your 4 ohm speaker would sound bad with the 15.2, it just won't open up to its full potential without good amplification.
I really haven't researched truly efficient, high ohm speakers because I have heard several of them at RMAF over the years and did not like them. The sound I prefer (in my price range) is Monitor Audio, B&W, Dynaudio and Quad's L-series, and these are not easily driven. Hopefully someone here can suggest efficient speakers.