Which USG Flex i should use

I raised my bandwith last month to 300/50 Mbit. Now the USG40 cannot handle this traffic anymore. Only 170-200Mbit, when i disable the security features and statistics. 

But i will not use a firewall a simple route to get the bandwith. Which USG Flex i should buy to handle the full amount of traffic with security features on, Traffic statistics on and VPN Service. 

But with TCP Traffic and not on UDP statistics in Datasheets - in a real world scenario. 

thanks a lot