The best is never cheap
Was using ER 6i's, for 3 years. 6 months ago, a professional audio/video installer recommended the ER 4P.
DO NOT PURCHASE THESE UNLESS YOU FIT THEM PROPERLY!
It takes several turns before they REALLY fit. It reminds me of the old Volkswagen Beetle; (airtight).
Once you filter out the outside world; WOW!
I listen to these M-F on the NYC subway. The majority of my IPod's 2,200 songs are Classic Rock; Beatles, Stones, Who, Clapton, etc.
If you want THUMPING bass, don't purchase; but if you want NATURAL bass, & GREAT midrange, these are exemplary.
New Beatles re-masters, downloaded on ITunes 9.0.2,sound incredible, without ear deafening volume.
You'll hear nuances, that you never knew existed.