VTL S-150 vs Audio Research GS-150 or Ref 150 SE

After auditioning numerous preamps I finally decided on an Audio Research Ref 6 (and it sounds wonderful)

i currently use a VTL S-150 amp, which I like a lot. but was wondering if there would be even better synergy with an Audio Research Ref 150SE or GS 150. 
 

PLEASE ONLY RESPOND if you have heard both the VTL S150 and either the AR Ref 150 or GS 150. I’m really interested in whether it’s worth selling the VTL to go all AR with the amplification. 

Note: I can’t audition either AR amp, that’s the reason for asking your assistance.