I have original VR-4's, would love to learn about upgrades. Why is OP's thread deleted 
I have a the VR-4's and about 6 or so years ago I sent them to VSA for upgrades. Cost was about $3,00.00
Whatever they did to them made a HUGE!!! and better sound. I'm not sure but I think that the upgrades to
VR-4's are no longer available.
I bought my VR-4's in 2006.
One more thing. When I got them back after the upgrades one of the base plates was broken. VSA said a
new one would cost $800.00 WHAT???? Hell I made a new one for $25.00. Still can't figure out why a new
one would cost $800.00 from VSA. It is a PUZZELEMENT!!!
Cheers
Charlie