If you are just looking to learn the OS and texture and model. Get a cheap O2. It will be slooow. But in order to do texture work the Octane has to have a texture card, which drives the price up. SE with texture or MXE.
O2 are going for hundreds on ebay. And they are good little boxes. They are much slower in comparision to today's pcs, but they are still reliable.
From what I understand XSI in particluar runs poorly on Irix (any box). But Maya and several compositing packages run very well.
If it matters at all..
Recently working in Maya on a heavy scene (nurbs and particles). My interactivity was much, much faster on the PC where I started the job. But it crapped out all the time. So, I moved over to a newer R12 O2. It was slower. I can not say it was faster. But Maya never crapped out. And the O2 got the job done.
