Amp Suggestion

Hi, I need some suggestions for amps to drive a pair of Von Schweikert VR6s. My current set up is Conrad Johnson 16LS pre and KR Enterprises VT-6000 mono bloc amps. My room size is approximately 26L x 17W x 9H, and listen to mostly Rock, Classical Rock, and Jazz music. I know that the VR6s are plus 90db efficiancy, but when driven to satisfactory levels the KR amps seem to lose some grip. I love the midrange and highs with this combination, but it does start to sound somewhat hard when the volume is turned up. Should I try solid state amps? Thanks in advance for any suggestions.