You have dedicated sound card? Like Creative X-Fi or something?
If so, go for the Carcharias, since the Carcharias would be able to
take advantage of the dedicated sound card. I have tried the
Carcharias with integrated sound, and it just sounds a lot better
with a dedicated sound card. If you haven't gotten a discrete sound
card, go for the Megalodon, since it comes with its own audio
synthesizer. I haven't really tried the Megalodon though, so don't
take my word for it. I have no idea how comfortable it is, but the
Carcharias definitely is.