[kaigan]

O2 and Octane are my second and first choice.

As someone who has both of those machines, I'd recommend the Octane. It's a good choice for a first SGI system as even lower-end configurations run IRIX fairly well and they're very upgradeable, too. Upgrading an O2 from an R5K to an R10K requires a number of parts that are harder to source. The Octane will do everything the O2 can and more.

One caveat is that the O2 can use some of its main RAM as texture memory, whereas the Octane needs to have it present on the graphics option. This might not matter to you if you're just using the system for general programming purposes, but if you want to do anything graphics-related, it would be good to have.