In any audio system, the weakest link among the equipments should be the loudspeakers.  Yet, it’s importance is sometimes ignored.  why is it the weakest link you might ask? Let’s look at the the distortion level of a typical equipment:

Head unit:  for a CD player, the distortion level on the RCA pre-out is very low, like 0.002%
But if you use the onboard amplifier to drive speaker, when cranked up, the distortion can become around 0.1%.  That’s why serious listeners would have additional amp to drive speakers.

Amplifiers: the amplifier on decks are around 0.1%, where a dedicated amp is usually operating at 0.01%

Loudspeakers:  you are typically looking at around 5%. That’s right, 5% distortion when play loud.

I think it’s because loudspeaker is the only equipment that converts electrical energy to mechanical energy that we can hear.  and by the design of it, we can get many type of distortions from it, such as harmonic distortions, cone break up, time delay, crossover design, phase distortion, etc.  That’s why in my opinion, it’s always worth it to buy more expensive component speakers.  With proper installation and tuning, it can ensure you several years of music enjoyment without the fatigue.  I have listed a couple of good component speakers that you might want to consider when shopping for one:

TS-C720PRS from Pioneer:

This is a very well designed and constructed pair of speaker.  Everything just sounded nice and natural when I listened it.  this would cost about $500 in retail, but you can get in for around $250 on ebay.