ssddx :
@op
if you liked cmss3d then you should like SBX which your motherboard has since they are both made by creative.
find a video which demonstrates SBX just as a test to be sure but i'm going to have to say that you might want to stick to your onboard sound and that whatever game you were testing just was a fluke and you need to run more tests.
while most certainly a good soundcard can give you a slight step up in sound, i'm not sure if its going to be necessary or not (but this depends on if you get headphones and which ones you get as well...see what i say below).
i'm going to combine the budget for headphones and soundcard as $300 since this will open up a few more options. some options however might exceed your budget by a little bit but are worth considering.
the audiotechnica ad700x $150 and ad900x $190 headphones are extremely bass light. most people who like decent bass response will say they are bass-less. such mid-high focus can be good for competitive gaming since bass can often cover up subtle clues like footsteps which can give you an edge however it also makes the game seem a bit less ...for lack of a better word... epic in terms of how it sucks you in with soundscape. the headphones here however do have one of the largest soundstages for great positional accuracy.
pretty much all headphones from AKG are similar in that they have very little bass and tend to be a bit sharp on the highs.
the beyerdynamic dt990pro 250 $200 is an open pair of headphones with a nice wide soundstage (but not quite as big as the ad700), clear sound and suprisingly deep bass for an open headphone. for the money its one of the better headphones to buy if you want bassy but open for gaming. they are known to be a bit bright in the highs though so you may want to tune them down with the EQ. they are known to be comfortable for people with glasses and large ears. they are however rather hard to drive so you'd want to use a soundcard like the creative z OR use a headphone amplifier between your onboard soundcard and headphones. a good headphone amp runs about $100 such as the schiit magni which would power them fine. lesser (cheaper) amps may not provide enough for these demanding headphones however its worthwhile given their sound.
the dt770 $200 is a closed design so lacks a large soundstage of open headphones which makes it not quite as ideal for gaming however many people still like them since they have a nice strong bass presence without getting sloppy or distorted in highs and mids. they have a V shaped sound profile accenting highs and lows with slightly recessed mids. they come in 32/80/250 flavors so some are easy to drive and some need a better amp. comfort is equal to the 990. generally the 770 is compared with the cheaper ath-m50 $100 but is superior to them given that it has a bit wider soundstage and a bit better sound quality but for double the price that should be the case.
the dt880 is similar to the above two but is neutral in sound profile and semi-open. its generally considered a bit more boring to listen to and more analytical.
the sennheiser hd598 $180 is an open pair of cans which doesnt have as wide of a soundstage as the ad700 and possibly not as good as the 990 but has more bass than the 700 but not as much as the 990. generally its considered a good gaming pair of headphones but for people looking for a more bassy sound they may find it slightly lacking. its easy to drive without a whole lot of power.
the hd558 $100 doesnt quite have the sound quality as the 598 or the soundstage but does have a bit more bass presence. its not really as good as the other cans listed here however for the price certainly not a bad option. its easy enough to drive without much power.
generally any of the cans above are fine with normal soundcards or onboard except any 250ohm models (specifically the 990pro which is only 250 or the 250 ohm 770).
Thanks for the detail. I will probably get the 990 pro's with the amp. I'll wait till the end of the year to see if either or drop in price. The cityscape uptowns are my first over ear headphones. I've only used ear buds in the past, (used the bose IE's for several years now.) I can't really compare over ears; where I live (Hawaii), the local bestbuy/sears/radioshack/walmart sample only Beats, Monsters, Sony's, and I really prefer my cityscapes over them.
Thing I'm wondering about is just the comparison between the 990's, amped, and the uptowns. The uptowns sound okay, but I'm wondering if the upgrade is worth $300. I know the argument is I pay for the experience, but would it be nearly $300 worth? The cityscapes are okay, but are just lacking bass and comfort (hawaii heat + leather enclosed pads), but I'd endure them if the quality in audio/comfort would be under 15-25% in comparison, to save $300.
Would be nice if you have sampled the uptowns, but if not, would you have an idea of how they would compare?