Amp for Usher BE-20 ?

Hi all,
Usher Be-20 owner out there, what amp you use to drive these beast ?
I have these speakers for couple days now - these have Diamond DMD tweeter. Still listening with Krell KSA-50S
Amps at hand including Atma-Sphere MA-1 and Cary 805C.
Pre-amp is Cary SLP-05
My listening habit is not too loud, and this Krell 50wpc is ok (only first light bias lid). But somehow I hear the low freq quite missing
I will rotate amps to test it out - Not sure if I need something with 200wpc, SS or tube ?
The DMD tweeter is somehow bright to my taste (got use to softdome tweeter, need time to adjust my hearing :)
Do you think tube amp will help smooth out the HF? I might try Cardas Ref cable to soothe the DMD ?
TIA