There are many fake Cx300 earphones around. The CX300 is decent enough but not great. I have had the CX300 for a few years. I don't know anything about the Q350. There are many other choices around the same price that are much better such as the Soundmagic E10, Meelectronics CW31 or M21, or the Audio Technica ATH-CKM50. If you can't get those, you might want to consider the Panasonic RP-HJE450.
You can try searching here for information on IEMs.