While I cannot answer 100% for Sunrise as I am using a Swisscom IB3 , I do get the full 2.5 Gbps up/down using this card in my QNAP TS-473. My understanding would be that if the Interface on the Sunrise Box is 10G , you will get a 10G Link ( and your Internet performance will be obviously less )
Similar to the answer from Ratfink71 - I did not have a very high-speed internet connection to test with.
However; I can confirm that while testing with a 10G router over LAN, this card does deliver 10GbE transfer rates to other devices that are having 10GbE Network cards. So, technically you should be good to go with this one.
Also, please note that you might need to enable jumbo frames with the highest possible value on both devices to reach the higher transfer speeds.