Wombat, I have the Turtle Beach X2 and I use it all the time with my PS3 and Xbox 360 (and Wii and PC and...) and it works great. Dead Space sounds awesome with them.
As for chat, you can use your X4 on the PS3. You need to get an USB soundcard.
Turtle Beach sells some, but I have
this one from monoprice.com. I have used it on the Killzone 2 multi-player beta and it works just fine.