Hi, I already have a pair of Klipsch S4 in-ear earphones and I am interested in getting myself a pair of closed back headphones that sound great and clear with pop, r&b, acoustic, and a bit of dubstep. My music source is the iPhone 4S and Fiio E6 amp. My budget is around $100. 
Also, how are the AKG K518, Marshall Major, Klipsch Image ONE?

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Never tried the Marshall's (though they're not worth it at the current price as far as I know) I will say that the Klipsch Image One's are bassier then the AKG k518's, which are a bit on the bassy side themselves. The K518's are my favorite among the headphones I own (then again my selection is pretty subpar) and they have a reasonable amount of balance along with that punch among the lows; really nice for a variety of genres (hosue -> dubstep, okay maybe that wasn't so wide).
 
I do consider the Image One's a little more V-Shaped, and they are a bit over your budget of $150, and if you want to go there I think the K181's are a better purchase for the money (in terms of value buy, K81's are better). Some others you should consider are the CAL!'s which are $55 on Amazon right now and the Audio Technica ATH-WS55 (which by the way had a pretty cool ad with that dubstep dancer - NONSTOP)

Are the AKGs On ear or Over ear

on ear i believe

Thanks

THe Koss DJ100 also has a reputation for being a very good value at ~$80. Check out ljokerl's portables review thread for more options.

I bought the k518le's already LOL
currently burning them in
sounds pretty good so far

are the sennheiser hd 518's any good or should i save my money and get the sennheiser hd 558's. is there a big difference? i want durable (metal headband prefeably) over ear headphones that have good bass and sound good with hip hop/rap, alternative, dubstep. I want them to sound better than beats solos. My price limit is $130. PLEASE HELP