I think audiophilia, to call it like a disease, totally ruins this hobby for most users without them even knowing. We are talking about an in ear monitor, of course you do not need an amplifier, though there are a very few exceptions. Of course your source should be loud enough but these earphones are made (!) to be used on everyday phones, notebooks etc.
It really makes me sad.
You are right. It's just that I am new to the audiophile world and just want to buy some good, cheap earphones. And then I get overwhelmed by all the different opinions and reviews. I was about to buy these on amazon when a reviewer, who seems to know what he is talking about says this:
THE 'COLORFUL ZST' IS EXCELLENT ON A SUFFICIENTLY POWERED SOURCE!
If you plan on hooking these up to your phone or an efficient DAP (20+ hrs of playback time) you'll miss out on the best that these have to offer. You'll miss the fullness and rumble in the low end which is the whole point of the DD in this hybrid. In addition, you will get slightly morelow end grunt with stock cables if that's your preference.
Playing the ZST through a smartphone or power efficient DAP will result in the lack of the incredibly clean and FULL low end. This means he/she will mostly hear frequencies ranging from 100hz to 20,000hz (everything below 80hz will seem vaguely absent) and then he/she will complain that the ZST doesn't have enough bass. Don't be a softhead! Play the ZST through an amplified source. If you don't have an amplified source you should pick up the KZ ED9. Yes, I may be coming across a bit rough, but I do it because I want you to remember this part of the review. A word to the wise is sufficient.
Full review here: https://goo.gl/J0iyeE