Your system requirements page recommends the ATI Fire Pro card, but when I check the AMD ATI sysreq page, it says no support for Macs. Does this mean we're to use Boot Camp Win only? And if I do, then why should I have the Mac version of Houdini?

The ATI Radeon HD 5870 graphics card in my new Mac Pro has been working really well with Houdini 11… I was concerned about this too at first and then saw that another Houdini user had reported some problems on the forum some months back and the developers fixed it. Here's a link to the post i read:
http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=20427&highlight=ati+radeon [sidefx.com]

I hope that helps…

Yes, thanks it does tell me that I can trust ATI … and the 5870 was what I was eyeballing. Unfortunately, Adobe says they don't support ATI cards, just Nvidia .. quite the limitation… but I think Premiere will run on an ATI anyway.

I'm not sure about older Adobe CS's but CS5 supports ATI Radeon…

http://www.adobe.com/products/aftereffects/opengl.html [adobe.com]

I've been successfully using Adobe CS5 on my system and it works great! It runs at 64bits! Also, Houdini's mantra in Apprentice HD is taking advantage of all my cores while rendering. I'm on a 3.33ghz 6-Core with 24 gigs of ram. Don't get any of your ram or harddrives from Apple… I got all my peripherals at the OWC. Let me know if you have any more questions. I went through a painstaking process while putting together my current system and learned many ins/outs.