I have the Thiel CS2.4's - oh and I have a REL 328 as well. I initially struggled a bit with brightness. It it was not the speakers. My final combination was a tube preamp (BAT VK3ix) with a SS amp with high current ability (Parasound A21). I know the Parasound isn't as glamorous as some other amps but boy does it get the job done. Also the REL sub helps the bottom end be more in overall tonal balance since the Thiels don't have deep thunderous bass. The final piece was using Purist speaker cable and Cardas Clear light interconnects.
I dont know know if this helps but I hope it gives you some thoughts
I dont know know if this helps but I hope it gives you some thoughts