There's been lots of threads recently, asking on advice on what headphones to buy. In this guide I will explain the things that go on with sound devices.
Alright. Firstly. Sound is a very subjective thing, everyone has their own taste and it's hard to know what's good or bad when it comes to sound, if you haven't heard a pair of really , really good headphones. You just have nothing to compare yours to, and when you hear an above-avarage headphone, you think that it's really really great.
That being said, it's time to move on to the brands.
Solid brands that have a great reputation behind them (Main Competitors): Beyerdynamic , Denon, AKG , Sennheiser, Grado (Current models may also appear as "Alessandro") Sony, Audio-technica , Fisher Audio .
Other Good brands that excel in certain areas: Forstex, Superlux, JVC, Phillips, Koss, Audeze, Hifiman, Probably many others, but cant remember them list them all, give me a poke in the comments)
Things to avoid: Skullcandy and Monster (Unless you're looking for a fragile fashion accessory), Bose, Anything branded as a 'Gaming Headset'.
Alright, now down to the headphones themselves, Most brands have actual headsets that sound awesome, but really, if you're looking for pure sound quality here's a list of things that really excel for their price:
Audio-Technica AD700 - 80$
These headphones are famous for their soundstage - It's way better then any fancy 7.1 Headset can do. What this does is give you a preciese 3d soundscape that's very accurate. Second only to 1000 buck headphones. these are THE choice for a multiplayer FPS. What sucks about them is that they barely have any bass. It feels like it's rumbling deep within the phone, it does not punch. However, it is accurate. Also some people complain about them being too big.
Sennheiser HD555 - a Hundred Dollah.
These headphones are sennheiser's starter 'audiophile' headphones. they have a very good soundstage but not quite as unlimited as the AD-700s. These are all-around good for pretty much everything. They can be modded to their greater variant the HD-595s(Or atleast close to it) Which will make the bass punch you. What sucks about them is that they get cracks quite easily, so handle with care!
Fisher Audio FA-011 - 120$
These are the best of both worlds - It's like someone combined the 555s and the AD700. It has a very wide soundstage along with punchy bass and overall pleasing sound. What sucks about them is that they're 120$ and hard to find.
Audio-Technica ATH-M50s - 155$
These are basically audio nirvana if you haven't listened to good headphones. You will hear new stuff and you will be amazed at how detailed recordings can be. What sucks about them is that you'll probably want a good amplifier or sound card to go with them. Also they're very picky about MP3 quality. Under 256Kbps is gonna sound underwhelming. They're also quite expensive. But if you fulfill all the criteria - they're audio nirvana .
Grado SR60i - 80ish dollars, hard to find in EU.
Famous for their price/performance ratio, even though those don't exist in the headphone world. They aren't fit for gaming, due to a lack of soundstage but if you're getting them for listening to aggressive music such as rock/metal - Oh wow, these babies will keep you happy. What sucks about them is that they're fairly uncomfortable and quite flimsy.
Superlux HD681 - 30-40$
Amazingly these chinese headphones sound pretty damn decent for the amount of money you pay for them. They also have a very large modding scene as does the grado SR60i. What sucks about them is that they need to be modded to be comfortable. Also they aren't widely available.
Forstex T50RP* - 80-110$, Hard to find.
What these headphones utilize is a different type of engineering - Planar magnetism. that makes them sound really damn smooth . Their bass packs a very hefty punch. They can be modified to the infamous 'Thunderpants', said to have amazing 500$-worthy properties. What sucks about them is that you will need a very good sound source as they follow the golden rule - Crap in, Major Crap out. Quality in, Major Quality out. They arent a very comfortable fit either, but the sound they produce even without a modification is considerably better than other mentioned headphones.
Pretty much those are my top recommendations, there's more expensive headphones but you shouldn't look for them here, this is just a beginner's guide.
As far as sound cards and amplifiers go : Either go with an Asus Xonar STX or a Fiio e7 + e9 combo and those should fit all your hifi needs . (Or you can even try to build your own! )
Also according to MMO-C users the asus Xense is a solid sound card when it comes to 5.1 dolby digital.
I've listened to most of the headphones I've listed here except for the Forstex M50. The 555 I listened to Wasn't modded either, so i've got no clue how it sounds personally post-mod but I have it on good authority that it makes the bass hit you and widens the soundstage.
Remember, before buying a headphone it doesnt hurt to listen to it at your nearby store.