That's a real good deal right there.  XSI are trying to bite into Autodesk's total dominance in the industry, now that they own both 3dsmax and Maya.  I think Lightwave, Cinema, and 3dsmax probably have the strongest base of independent artists or hobbyists using their software, and XSI probably sees money in that.  Regardless, it's a great offer, and if I were you, I wouldn't think twice.  The only thing you might regret is that XSI is nowhere near as user-friendly as 3dsmax, and there isn't near the level of online support for it, in regards to tutorials or forums.  As a newby to high end 3d, you'd be almost on your own with the learning curve compared to the stong online support for apps like 3dsMax, Cinema, or Lightwave.  Something to consider anyway.