Power Amp or Mono blocks for JBL K2 S9900

Looking for recommendations from anyone familiar with the speakers. Room is fairly treated. An all digital setup using Lumin streamer. I currently use an Esoteric Preamp along with Krell FPB400cx with fairly pleasing results. Wondering what power amps or mono blocks go well with the speakers or will provide with additional power / improvements?

Thanks in Advance.