I have the infinity system, first the dash speakers pooched, replaced them with 2 audiofrogs each side. That was a remarkable improvement. But I think you need be careful, you cannot just replace the speakers with any speaker and see an improvement and you may see it to be worse. i.e the door speakers play pretty low, to sub range, so only the right kind of speaker would be suitable speaker and make an improvement.
Even though all the factory speakers are cheaply made, the systems and all the speakers were carefully tuned to work with the amp etc. So buying a $50 dollar speaker will not automatically give you an improvement over the $2 speaker it is replacing and quite likely would be worse.
To make the right decision, make sure the replacement speaker is of the right ohms first, and capable of playing the same range. Which is why I had to replace 1 speaker each side of the dash, with 2 speakers.
Now my sub seems to on its way out, hope this option works good, as the audiofrog is expensive, but may be worth it.