Hey there,
If you do not insist on tools, I will suggest you use Nginx as your cache server.
It's already working with Magento perfect and there are way more options, sysadmins, and best practices to implement Nginx as your HTTP cache server.
Also, Nginx works way better than varnish in high scale level. You don't have to write difficult and complicated rules and ACLs in Nginx.
I will be available for little chat in Facetime / Whatsapp or here over text if you want :)
Best Regards
Daniel