Don't know the LK2, but had a Kairn and LK100.
The Kairn will connect to 3 amps, hence the 3 RCA outputs. You only need one set to the LK2. You should pick either (doesn't matter which) RCA out on the Kairn and connect corresponding XLR with your cables.
The Kairn will connect to 3 amps, hence the 3 RCA outputs. You only need one set to the LK2. You should pick either (doesn't matter which) RCA out on the Kairn and connect corresponding XLR with your cables.