My D600 remote still works but it has terrible range so I have to be right next to the speaker to use it. But I got a GE universal remote for $5 at Big Lots and was able to get it to control my speakers by having it search through all the codes it knows until one works. I think the only functions that work are volume and muting but those are the only ones I need. I leave all the other settings alone on my speakers. So it's probably a less complete solution than spending $150 on a Logitech Harmony 520 but it does everything I need and it only cost $5.

P.S. If you ever need your D600 speakers repaired, Meridian will no longer do it for you but I found a neighbor who was able to do it for me.