As an update, my collection of DTS 5.1 discs will not work in the Krell system. I have quite a varied collection, and only 3 of the discs will play. And of the 3 discs, none will record on the HDD. That said, none would record on my old RLXs either, but it seems that one advantage of the ELS system over the Krell was its ability to play all DTS 5.1 material. Go figure.