It sounds like it would help if you look at the bigger picture.
If you are setting up a renderfarm w/ 30 dual processor machines....
are those machines windows, linux or irix?
how will your desktop workstation interact with the farm?
Are your frames going to video?
What kind of video system, Avid, Discreet, other?
From my experience, we use Maya on Irix and render on Linux. The 2 work really well together. We also do our video in a Irix Discreet system. We recently added a Win2K machine (SGI branded) to the mix. It is faster when working interactively in Maya than the Octanes and O2s but it was a little tricky getting it to play along on the network with shared storage.
There fewer choices for renderfarm manangement software on Linux and Irix. There are more for Windows. If you are rendering on Irix then the Alias|Wavefront built in distributor should work. On the SGI web page they sell refurbed Origin servers and pretty good prices.
If you do not need the second processor in the desktop machine then I would look at the SGI Fuel workstation same V10 or V12 graphics in Octane2 at a much cheaper price tag. Although the price is still not as cheap as a PC with Wildcat.
I would not get the Octane2 unless you are using it for video at HD or film res.
SGI Irix , SGI hardware and SGI support are all very very reliable and stable. SGI stuff is expensive to buy and expensive to maintain. Yearly service contracts are pricey. And they are not as fast as a homebuilt Pc with a good graphics card. However, when we put our jobs, our reputation and our money on the line, I trust SGI. We still use an original Octane like 7 years old.. still cranking. SGI support has bailed me out several times.
I would think the Fuel or Octane2 would work out. But like I said first look at your overall facility and see what will work best now and in the future.
Hope it helps.