YUIN PK3 Earbuds

I bought both the PK1 and the PK3 because I wanted to see what the difference was.  The PK1's sounded better at first and I didn't want to spend too much time using the PK3 if I was going to sell them to a friend at work.  BUT...that friend bought them and burned them in.  They now sound GREAT at $40.  Other people who sit next to him now want them.  I decided to keep the PK1 and will buy them an amp which they need according to EVERYONE to drive properly.  My recommendation, though, from earbuds you got from your player is to buy these and live with them for a while.  Enjoy them and then see if you need more.  I've tasted other good headphones and so I wanted the cleaner PK1's and will buy an amp to drive them properly.  (An amp is needed if the headphones need more voltage or more current to be able to handle swings in voltage or enough voltage to drive inefficient headphones.  It is not just about volume but about enough capacity to deliver clean and sufficient power for complex input/output.)  

BTW, design gets good marks because they feel good in the hand and they don't draw attention.

I may buy the PK3 again...and love them for working out and grabbing them on the go without an amp.