Solid state warm up?

I recently Put in a BAT vk-250SE with bat pack into my system to power Dynaudio Contour S 3.4 speakers. I was using a B&K reference amp with pretty good results, but I wanted more detail and subtlety. I got both, but I also got a darker, almost mushy sound. Some material is worse than others. I have pulled the speakers a few more inches from the back wall which helped a bit. The sound may actually get better the longer the amP is on...hours. Could the amp just need to warm-up and maybe be left on 24/7? It does get quite warm. I use the 12v trigger to put it in standby. Any ideas?