I just find it hard to believe an ER4P can kill a Livewires, unless the fit is not good. Not because it is a single driver, but because of all the descriptions of the ER4P sound reads to me like they are lacking something the Livewires have - bass.
In terms of making music as a whole, my Livewires T1 beat my SE530 and Triple.fi 10 Pro, as well as my IM716 with podectomy, ER6i, Denon C700, Super.fi 5 Pro, SE310, E4c (borrowed from my friend that bought them from me) and any other IEM I have owned.
Now, MANY of those above are very musical and enjoyable, but the Livewires simply disappear and leave an open window into the music without veil or coloration. The only thing I've heard that has the transparency, accuracy, and realism of the Livewires was the Westone 3 that I demo'd back in September. I loved the Westone 3 as they also had a little more bass impact, and with the Comply tips they were very comfortable. However, I think the Westone 3 were a little brighter in the 4Khz range which on occasion could make my ears resonate at louder volumes. So, the Livewires may actually be a little smoother, based on my memory (which I am sure will be called into question and criticized, as is the nature of head-Fi). Once the Westone 3 are available they will also cost $150 more than the Livewires, so you get what you pay for.
One more thing I should add. I was more disappointed with my SE530 that I kept than I was with the triple.fi 10 Pro that I traded towards electrostats. The SE530 highs were slightly rolled off, and while changing tips could boost the highs it could also either hurt the bass or could add un-natural coloration to the upper mids lower treble. I also broke a nozzle tip off too easily once, and SE530 have a history of their cable self-destructing without being abused. However, when using the Black foam tips they were more comfortable to my ears, and they were more transparent and uncolored than Triple.fi 10 Pro. The Triple.fi 10 Pro seemed to have an upper bass coloration that sounded similar to an small acoustic suspension speaker box that was the wrong size. It destroyed the transparency for me.