Need help selecting a new pair of headphones

in case you were not aware, the hd518, hd558 and hd598 all share the same exact driver. the difference in sound (hd518 having most bass and least soundstage with the hd598 being most neutral with largest soundstage) is due to the shape of the headphones. also, most headphones which end in 6.3mm (1/4") plugs have screw off caps. unless i'm mistaken http/cdn.head-fi.org/0/02/472x500px-02690849_stereo-jacks2.jpg is what your cable end would look like (do check up on it).

cant say i know much about the wireless options but hd598 is superior to the hd558.

if this is a set to stay at home, perhaps you want to check out other options like the ad500/700/900x (if you like a bass light sound that is advantageous in games). nice wide soundstage however poor low end bass (but decent mid bass). the akg and grado cans are similar.

or, if you have an amplifier (or can set aside money for one) the dt990 (or dt880 if you wanted a neutral sound signature) are great. the 990 has a wide soundstage, v-shaped (slightly recessed mids with more bass/treble) signature and is fairly bassy for being open. known for comfort. they DO need an amplifier or powerful soundcard to sound their best but for at-home cans are worth thinking about.

2) you might be right about it being 1/4 only but with an adapter. according to http/www.head-fi.org/t/598506/why-do-the-sennheiser-hd558-hd598-ship-with-a-1-4-headphone-jack that makes sense. i do know other headphones come with a screw off design, why senns do not is silly. i've heard senn makes a hd598 cable for 3.5mm (1/8) available though. unfortunately seems you're not lucky and they dont have a screw off design like some other headphone designs do (such as the ones i own and use).

3) sennheisers tend to be a bit more laid back. this means that they do not sound as energetic or detailed as other cans are, however are more easy listening for long periods of time. both bass and treble are more subdued compared with some other cans, they are closer to neutral than anything. i suppose another word you could use for them is slow. none of that is bad, if you're into that kind of sound and they do make good headphones for someone who is not sure what they want. your call about what you want although i would highly suggest giving those cans a listen at a local store if possible the beyers really are nice vibrant energetic sounding headphones (though not sure if you actually prefer the laid back character of the senns...some certainly quite enjoy that).

4) sounds like a receiver to me (i have one sitting on my desk... you can see it in build photos in sig) which often have a 1/4 jack on the front. what i was talking about is a more manageable sized box like the fiio e09k, schiit magni, or similar sized box. a good internal soundcard like the soundblaster z would also work. mostly this would be if you picked a beyerdynamic can up since they are harder to drive.

perhaps the best bang/buck are the hd518's in terms of audio quality per dollar. i've heard of people getting them and just putting nicer pads on. what you get by jumping up to the 598 level is certainly a bit more soundstaging and more neutral sound given the design but also a bit more build quality and better pads. personally i think the 598's are a quite hideous color (opinion!) but thats just me.

not trying to push you one way or the other. just throwing some opinions and thoughts out there.