I have a pair of OMEN MK.II with upgrades that I purchased directly from Zu Audio. I've listened to them using the various amps or integrated amps I have (both tube and SS). The speakers sound good regardless of the amp I use.
My amplifiers are as follows in no special order:
Plinius SA Reference
Allnic T-1500
Conrad Johnson Classic Sixty SE
Luxman 590 AXII
Class D Audio SDS