Softimage Xsi: SI|3D differences

I've noticed the price drop in Soft.|3D but i haven't seen anything (and I don't even know if this matters anymore) if that is the price for Base or Extreme. I'm assuming Base. But then again, I can't find any reference to there being more than one version of 3D being made anymore. Do they still make Base and Extreme, or is it just one version now? If they do make different versions, what are the main differences between them?