UE900 is fairly analytical with some warmth. They also have good sound stage, making it suitable for jpop and classical. They have good comfort and isolation along with great build quality. If you want more analytical kind of sound, look at heir 4.ai. They use TWFK, which are known to be clear and analytical.
I think cMoy would pair well(from reviews on their sound sig) and I can't comment on iPod classic because I don't have one.
SE215LTD has enhanced bass. It has more bass and more extended bass. K and CL is just a color difference. K is black and CL is clear.
If you like S4, you like lots of bass. VModa M100(lacks isolation), SE215LTD(you need more bass than normal SE215), M80(lacks isolation), and Momentum is my suggestion.