i have travelled a similar path. upgraded earphones make a huge difference, and i would strongly suggest you check out options among Westone's alternatives. The UM2 was one of my favorites. I tried just about everything that Shure had to offer, and didn't care for any of them.
All of that said, unless you are planning to (1) use an external amp (even a very small one) and (2) rip in a lossless format, i wouldn't invest heavily in fancy earphones as your upside will be very limited.
All of that said, unless you are planning to (1) use an external amp (even a very small one) and (2) rip in a lossless format, i wouldn't invest heavily in fancy earphones as your upside will be very limited.