Are these 2 OHM speakers? I do not believe they are as there are only a few who make them. I am thinking Pioneer are 4 OHM. If you are using the stock HD head unit and/or Amp, the volume output is going to be significantly less as HD components are 2 OHM. Went down this road a year ago.
They are 4 OHMs, I went with the 4 instead of the 2 OHMs because i find they have a better quality sound more depth to the sound (at least for me they do)
I checked into the difference between the two and it says it's roughly 2.5dB difference in loudness not that I can notice that my hearing isn't that fine tuned. But I can notice the depth and quality of the sound.
From what I was reading 2 OHM speakers also don't last as long as 4 OHM one. That could be why I was finding the sound on mine to be getting sort of tinny sound (that's the best way I can describe it) I would have to turn it off. On some certain songs the sound was rubbish yet on another the sound was better.
So I'll try out these ones and see how they perform then go from there.
BTW,....I always listen to my tunes when riding and always though the external speakers.