The louder you play, the less you can tell the difference. Bass is probably what you're refering to.
Last time I looked for speakers in the 400$ (each) range , I could still say that some combo was more clear in the mid range or the highs. It's all about what music you use to test it, some recording (great voices mostly) have very very clear mids which you can tell the difference between a set, the best really open up. Others have detail in the highs that are a lot harder to hear on speakers that are weak there. I don't know past what point you cannot tell the difference, but I do know it's not 150$.
Last time I looked for speakers in the 400$ (each) range , I could still say that some combo was more clear in the mid range or the highs. It's all about what music you use to test it, some recording (great voices mostly) have very very clear mids which you can tell the difference between a set, the best really open up. Others have detail in the highs that are a lot harder to hear on speakers that are weak there. I don't know past what point you cannot tell the difference, but I do know it's not 150$.