or - you can simply purchase a QNAP QXG-10G2T, which is a compatible dual port 10G card, that I assure you works. You should have purchased that when you first got the TVS-h874. OR, if you intend on adding in a 3rd computer in the future - just leave what you have, and purchase a small 10G switch, so you will be set for the future, instead of making lots of tiny purchases (that add up to the price of a small 10G switch).
Bob