I have a Hyper X cloud 2 USB headset. I want to upgrade my sound and Microphone quality. Will this be a big upgrade if I go for ether sennheisers. I own a MSI gaming 6 Motherboard so to anyone that knows I don't know if the sound will be decent if I directly plug into them. the Pc version comes with USB , would it be an upgrade if I just leave the USB on them. If go for the HD598 I'm going to probably end up getting a sound card from what people are telling me then a mod mic or a separate desktop mic. My uses for this are gaming, Music and Movies. HD598 is $150 and Pc363d is $200
pc363 and game zero are very similar. both have bass light sound.
the hd598 is going to be a bit more neutral in comparision which means a bit more bass without them being bassy.
soundcard that comes with the pc363 is fair but using a good soundcard instead would be loads better. your onboard may or may not be fine.. honestly it varies so much its hard to tell without you testing the quality. hd598 may be able to be driven by your onboard but again you need to check. a soundcard is certainly not a bad idea but i would see where you stand first before thinking of upgrading.
modmic is good if you go the headphone route.
its an upgrade, but as far as "big" upgrade that depends on your sense of audio quality and how much it matters to you and your preferences.
if you like bass light sound (zero/pc363) you would also want to look at the ad500x and ad700x.