If you use Bookworm and use the built-in support for espeak, you can get up to 600 words per minute or so. Dectalk can go well over 900 words per minute. As far as I know, cocoa tops out at around 500 words per minute. So all of the options accept piper should be fine for you.
Also, if you don’t feel comfortable building bookworm from source yourself, and you feel like you can trust me, Here’s a build of the latest bookworm code from github for 64-bit Windows: https://www.sendspace.com/pro/dl/rd388d