R8000 Nighthawk Not Capable of 1Gbps WAN

So I've been doing some digging and found that the R8000 Netgear Nighthawk supports 1Gbps on the WAN port but the problem when you use the Router with PPPoE, CTF is disabled and/or the CPU cannot keep up with the full bandwidth. Hence you end up with 450-500Mbps instead of the full 900-950Mbps achievable with my ISP's router. 

I've found that in the firmeare version 1.0.3.4 this was disabled 'Fixes the Telefonica IPTV crash issue by disabling the CTF in PPPoE mode when IPTV/VLAN is enabled'. Therefore my question is if I use a firmware version older than this, would the router be able to utilize the full capabilities of the line?

I'm at work at the moment and can't test but looking forward to testing when I get home. Probably with firmware version 1.0.3.36. I should also mention, that I am not using Dynamic DNS, VPN, Traffic Meter or any of the other extra features on the router. The only things enabled are Wireless 2.4Ghz and I have combined the 2x 5Ghz bands into one. There is also 3 of the LAN ports being using which serve a Gigibit switch in another room.

It's disappointing that this router can't achieve the full line speed, expecially for the price bracket and overall capabilities, I really don't want to have to switch it out.

Thanks for any and all suggestions.