In 2010 a collection of sound designers were finding that they were getting asked to design sound environments for exhibitions, installations, museums and the like, they quickly discovered that the tools required for this were pretty specialised and therefore costly. So they decided to would make their own.
What they came up with was The Sound of the Mountain or MNTN. Its an environment for designing multi speaker setups and also for placing sound sources inside that space. MNTN offers for 2channel binaural HRTF headphone rendering which means you can build the environment just working on headphones then connect your multiple speakers at the time of installation. It also supports bass management, Youtube 360 ambisonics, 5.1, 7.1 and 12.1 (in higher output licenses). Additional outputs can be added as required.
Their pricing is based on the number of sound outputs you need. Starting at £149 for a 2ch system with price scaling up depending on the number of outputs you need up to £1,1199 for a full 64 output system. You can also buy a license for the 64 channel system for one year for £299. I guess it makes sense as you can get started on a 2ch system, then upgrade as your needs expand.
The MNTN system runs as a standalone application which then connects via your DAW with the MNTN plug-in (AAX/AU/VST) to route to as many outputs as you need. MNTN state that they have successfully run 64 sound objects on a 32 channel output system with an early macbook Pro 2.8gHz i7. You need El Capitan, with no reported problems on Sierra- and it goes without saying this is an OS X only app.
There is a full 30 day trial available via the website: MNTN.rocks