Nice gear! yep get your preamp replaced, maybe tubes? and you will be very happy NAD is a solid cost effective product but your gear deserves better, I use the Aragon 4004MKII but I am Horizontal Bi-Amping, its a nice amp.
You are very lucky to have your own room and be able to set speakers out in the room so the performance is optimal, I can always dream right? VERY NICE ~!
