I initially ran my VR4's with an Aragon 8008bb on the bottom and Manley Neo-Classic 250 monoblock tube amps on the top.
IT IS NOT NECESSARY TO BI-AMP THESE SPEAKERS!
I now run them with Parasound Halo JC-1's (bi-wired) and an ARC LS25 mk1 with XLR IC's between the pre and amps (XLR connection with these amps is absolutely essential).
This combo is a much better setup than the bi-amp scenario, IMO.