What to upgrade next?

I think you're getting a lot of misleading advice. There is absolutely no reason to replace your cables, nor add fancy power cords or line conditioners. You already have a great system and assuming you've set it up properly, it's sound will not be readily improved without wholesale changes. Changing cables and such may slightly change the sound, but it's unlikely to really improve anything. I have three suggestions. First, consider some professionally designed acoustical room treatments. Dollar for dollar it's the most cost effective money spent. Second, look at getting a high quality rack and speaker stands (Sistrum, Mapleshade, Solid Steel, etc.). Third, replace your CD player with either the Linn Unidisk or Teac/Esoteric DV50. Both players are universal machines that will playback any format which will allow you to run hi-rez SACD and DVD-A digital through your system.