First off, if you are going to lean towards the Senn's, I would go for the IE80, not the IE8..............the 80 still has the big bass, but is a little more present in the mids, and to my ears, has a bit more 12K+ Hz presence and instrument separation.
Also, with price not being that big of a factor if you're looking into Ie8's, I would also consider the Westone UM3x or Westone 3 or 4. I don't think people give the UM3x credit for having great bass, along with amazing separation, clarity, and soundstage. In fact, if you're going to amp whichever ones you buy, I don't think you can find a better universal than the UM3x. The 3 and 4 lean a little more toward the bottom heavy sound, but they aren't muddied and still produce great mids and high end sparkle. They are more tuned toward a "fun" sound, but don't let that give you the impression that the UM3 can't be fun, too.
The Sony MDR-ex1000's are good, but I've just never been completely satisfied with any sony earphones, including those.
ETA: I'm not sure if you prefer dynamic drivers to BA's, but I generally feel like if you don't have a big collection of IEM's and you are going to spend $250+ on a set, your best bet besides customs, is to go with the best multi BA IEM you can afford.
I, too, would love to try a hybrid monitor. Right now I'm saving up for my JH18's, but after that, I'm being undeniably drawn to the Unique Melody Merlins.
Edited by ParadigmLost - 3/22/12 at 5:34am