The cx300 are better than you get with the stock iPod buds no question.I used them for a month to try out as a loaner and found them very mid orientated,lows were bloated.as well,when walking,I could hear plenty of ambient noise around me,wind,traffic,etc..Cables very thin and prone to break.
There are much better than those out there.
In the world of headphones and amplifiers,there are so many out there and so many small manufactures that it can hard to keep up.sound is very subjective and synergy is important between components. One headphone amp may or may not sound good with a specific headphone and vice versa.
Pete,I think the etymotic is incredibly detailed but not for everyone. Note that I have several and all have different tones,I tend to enjoy a slightly darker warmer sound,therefore the sennheiser hd 600 and westone um2.I tried those shures and they were not for me.
In hifi,you generally fall into the grado or sennheiser camp sound signature.
Iem universal- Shure or westone.
But again so many out there,dozens and most on the higher end are all good.