I agree with SolidVictory that it might be nice to slowly move up, as both he and I did, which did allow me to better appreciate the SM3. However, I did hear the universal version of the UE11 at Can Jam in 2009 and was blown away, knowing they were so much better than my IE8, with a much better space, clarity, and bass impact (yes, BA bass impact). I had fun along the way, but if I got the SM3 back then (they weren't available) and was done, that would have been fine also. The SM3's gave me the same sense of power that I have only had surpassed by the FX700, but not by much.
As far as BAs vs dynamics, insertion depth and especially seal play a huge role in the amount and quality of bass. I do have to admit, the SM3 is the first universal BA that has had what I would term visceral bass. It can be done! And from what I understand, all the high end customs also are capable of the same. I am looking forward to hearing the EM3 Pro, as it has dual low frequency drivers; I would imagine it really can pump out the bass!
So, assuming you do want to spend the money, here are my recommendations:
SM3 - best true to the recording, good or bad, that I have heard. Some of my metal is poorly mastered, and I really know it with the SM3 (although every high end IEM is much more revealing than the v-moda! These can pump out very strong bass and have the best space I have heard from an IEM, period. Very liquid presentation and comfortable. These have the best isolation of the IEMs I am listing here.
FX700 - The FX700 is an excellent IEM and has great detail and clarity. The sound signature is V shaped, meaning the bass and treble are both enhanced. Nice wide soundstage, but isolation isn't the best. Best dynamic I have heard, but not neutral.
MTPC - Nice balance, but does enhance the bass. With any source other than my Rx, the soundstage is pretty small in comparison with the rest of my top-tier IEMs. Compared to the SM3, these sound a little muddy and not as transparent or clear as the FX700. A little on the slow side in comparison with the others.
RE252 - Since I cut off the ear guides and can get these things deeper in my ears, I have been impressed. Think the Copper with less bass and additional clarity and speed. I like these better than the IE8 for the most part.
I was thinking of posting a 'why not' list, but I don't want to go down that road. You can PM me if you want some reasoning behind my thoughts. And please do read the top-tier thread.
