I'm currently looking for a nice pair of headphones and an amp, my budget is $200 for headphones and $120 for the amp. I like clarity with some good bass, not too much to make it sound muddy and distorted. I like to hear good detail in music and games. I'm also looking to have virtual "surround sound". Right now I'm looking at the HD598, AKG-K701, ATH-M50X, and ATH-AD900X. I'm mostly looking for headphones for gaming and music. Currently I have a pair of Logitech G930s and the sound quality of the "surround" is pretty good for the price, but I'm looking to upgrade.
m50x has small soundstage, making it not ideal for gaming. i have the older m50s and while i do like it, i'm being honest here. they do have a nice warm "bassy" but not too crazy sound. bass is slightly bloated but not bad. these can hit sub-bass levels unlike many non-basscannon class cans so feel much heavier in bass.
when i say bassy i mean more than neutral but not bass-cannon heavily distorted levels. bass on bassy headphones can range from tight to a little bloated. you should specify what kind of bass levels you're looking for..specifically.
k701 has sharp treble, is hard to drive without a good amplifier, fairly neutral with some bass (better than ad-series but not bassy either). a bit punchy but not much depth to bass.
hd598 is mellow and easy listening, fairly neutral, and while not the most detailed is not fatiguing. a good all-rounder.
ad900x is more mellow than the akg cans but still fairly bright. they are still a little light on bass but are far more bassy than the ad700x and ad500x and are more similar to the hd598 and k701 levels. punchy yes but not much depth to bass.
you did not list the dt990 or dt880 so i will include them in your list. the dt990 is heavily v shaped with bright sparkly detailed treble, good deep bass levels for open cans and nice soundstage. the dt880 is similar in nature but is more neutral with less bass and slightly less bright treble.
as for the amp, what you need depends on the headphone you pick. some will run find from a soundcard like the creative z, while others will absolutely require a dedicated amplifier. also, it might be a good idea to experiment with razers free virtual surround right now and see if you like it or note if your onboard audio quality is any decent (does it crackle, distort, buzz, etc) as this could mean the difference between using that + external amp or needing to have a dac or soundcard. again, specifics are helpful as we are not there to see what you have or like.
almost identical to the new m50x in sound quality but cheaper with a long straight non removable cable. as stated in prior post i have one. while its not a bad can its really not ideal for gaming unless you do not care about soundstaging depth of field.