Looking to upgrade portable audio system

[sparkyuk]

At present all of my audio gear is set up for my laptop and is simply not practical for portable use. As I spend a fair amount of time using my laptop & Gaming I own a pair of Steelseries Siberia V2's (SteelSeries – SteelSeries Siberia V2) and the Siberia USB Sound card (SteelSeries – SteelSeries Siberia USB Soundcard). Note that I'm not looking to replace my computer headset, just providing an example of the audio kit I use at the moment.

The sound card is on its way out though, so that's another factor i'm considering here. I have tried to use the Siberia headset for both my phone and Ipod but the sound quality in comparison to the laptop is ridiculously poor and they are far too chunky to wear when travelling about so this has all led me to consider buying a new set of audio goodies

The buds I use at the moment are the Skullcandy Ink'd, though these have made me realise that I'm not a fan of in-ear earphones so these are not an option for me.

What I am considering at the moment;

Sennheiser Px100-II
Portable FiiO E5 or E7 (am yet undecided and still unsure whether this is a suitable choice).
A line out cable? - Do these really make a difference or is one necessary only for high end gear?

Ideally I'm budgeted of a maximum of £100 - but this figure is flexible; I want the ideal cheap solution with amazing sound which I know is impossible to get, but as close to it as possible would be brilliant.

Music wise I listen to a wide range of genres; dubstep, drum and base, pop, some classical and trance and as such I feel that a all rounded set of headphones would be the most suitable for me.

Cheers for reading and any help is appreciated in helping me make my decision <3

Sparky