KEF LS50 Wireless connection to Node 2?

I just got a great deal on a pair of KEF LS50 Wireless speakers and have decided to use my Node 2 with them. What's the best connection I should use? The KEFs have an option of USB in but the Node doesn't have USB out, just RCA, Toslink and coaxial. The KEFs don't have a coaxial input. Should I just go Toslink with something like a Lifatec cable or RCA?

Thanks for any input.