For anyone thinking about getting the PFE's as an upgrade, I'd recommend them generally. As the 139 pages previously attest, they are technically very good (in my opinion not being an audiophile).
I tried them with just the iPod phone out - they were good, big jump up from the standards (can't ever believe I used them for so long). I needed more punch and did not think they were being driven hard enough so purchased the Fiio E5 amp - good upgrade, noticeable boost in the lower frequencies and more dynamic 'full' sound.
However, the PFEs failed on me twice (both times the right ear only put out 5-10% volume) and I sent them back. I thought i'd persevere and went back for a third pair (the latest version with thicker 'rubber' like cable) and at the same time, purchased a Graham Slee Voyager amp - Received both, paired them up with a iBasso line out docking cable and.....
Unbelievable difference!!
The sound stage could be described as narrow (no big deal if you don't care or appreciate it - but you soon will) but the seperation of instruments, accuracy of vocals and solid low frequency performance continues to amaze me. What was once just 'noise' is now clearly music as it should be heard
Just make sure if you rip your own CDs or records go from FLAC/APE to AAC - it really does make a big difference.
Unfortunately, I've had the right ear go yet again - it had me thinking though, previous pages mentioned moisture? They do go in my ears first thing in the morning on the way to work (after shower etc). They are working again so i'll see how they go.
The PFE's really are good - and thanks Head-Fi folks, I lurked on here for weeks before making a decision - time well spent.