Are you in the position you actually need a sustained 1GB of WAN traffic
There is also no law that says that site-2-site traffic has to use the same appliance than internet/guest internet traffic.
You could very well have your core switching have internal routes pointing towards SD-WAN MX appliances (enterprise license) and have internet traffic pointing towards another pair of MX'es (different org with advanced license).
I know it is expensive but having a 1 GB link is an investment.