As much as I love Pioneer products, the coax speakers I installed in the rear of my GE8 2009 sport, are not better than the factory ones. I expected them to sound better as most aftermarket stereo components are better.
They lack the punch the others did and I believe I'm going back to the factory ones as soon as I feel like yanking the door panels again. Just didn't want someone making the same mistake. Mine was relatively inexpensive at $50 for the pioneer replacements and I might find another use for them.
I have a Pioneer 3100 HU which sounds great with the factory speakers. I did replace the tweeters and the Pioneers ones are a tad more sharp. If anyone wants to see pics of what the factory ones look like let me know and I'll post.

 

I had to learn that same lesson in my tbird. I just couldn't get away with doing it on the cheap. It just resulted in wasted money and replaced components.

From my experience with the fit:

1. Must buy component speakers not coaxial (heck the sport has a perfect mount for the tweeter already). Infinity kappa perfects ROCK.
2. You must have an external amplifier. No HU is going to put out enough power for good speakers. I'm running 75rms 150 peak PER speaker and could still use MOAR.
3. Don't bother with the rear speakers.
4. Get some sort of subwoofer. Anything will help. From my experience go with a single sealed 10". However if space is not a concern 2 12"s will do great with low frequency extension. Still recommend a compact sealed box vs a ported box after using my epic 4.4 cubes ported 34hz ptf box and switching to a sealed box the sq increase is amazing.
5. Don't buy audio components that are sold at walmart unless you understand you will replace it someday in disgust.

 

Well that sucks to hear. Sorry about the problem. Hope you find something better.

 

i think a good headunit is all you need for a decent sound upgrade. keep the factory speakers.

 

i like to play the factory speakers with +5 both Bass & treb, and keep the volume no more then 16. This acts like a high power feature

 

Surprisingly, factory speakers work for me just fine.