I'm looking to build a PC to use for Houdini and was wondering what would be the main things I want to make sure I include in my build. I'm really just starting to research this at this point so I'm very open to suggestions.
thanks!

Simulations need memory so at least 24GB or more.
Simulations need CPU count so at least 8 core or more.
Some simulations can leverage the GPU so get an nVidia card with at least 2GB ram preferably 4GB or more. Avoid the wimpy ones with low core count (you can check core count on the specifications page, for a given card, on the nVidia site) or the mobile version of a card.
Intel is better than AMD but AMD does indeed work.
Try to build your system using SSD drives.
Make sure the motherboard you get supports USB 3.0 and SATA3 support.

As of H14 there are problems with OSX opengl drivers for intel cards so if you go the Apple route avoid any product with an intel graphics chip, the I7 cpu is fine of course.

Awesome, thanks for that info, that's very helpful.

I've been a Mac user for years, I do motion graphics primarily but I've started learning and using Houdini and I haven't been happy with the performance I've been getting on a Mac so I was going to try and see how it fares on PC.