I also got V4s with Yamaha s500 amp, and biwired.
I was thinking of upgrading , so I tested a pair of DC6Ts on the same system.
Very little difference at this level (eg Yamaha amp and CD player).
V4 has a deeper Bass, whilst the Alu tweeter of teh dc6t gives a little more clairty or volume at teh higehr end. That's about it. And I agree with the previous poster, that the V4 gives better output, and better sound quality a low volume, than the Dc6ts.
So if you don't mind the shape and the awkward rawplugs on the grill, the V4 is a better deal. If you liek a softer sound, and are willing to pay at least twice as much, the DC6t is your product, although the espresso veneer finish is very coarse and rough.
Also , the V4 cable plugs are far easier to use than the Dc6T.