Dif between a VTL 5.5 and 6.5?

I own a VTL 5.5. I also own an ARC Ref 3.

The ARC is fantastic, but I find the VTL has more midrange and is somewhat more synergistic with my system... but the VTL sounds a little dirty in comparison.

So I'm wondering what I would gain if tried the 6.5. Can anyone shed some light on the differences between the 5.5 and 6.5?

hi there. call vtl directly for the differences btwn the 5.5 and 6.5. i think the 6.5 is in a different league entirely.it is a superb preamp. see my review on this site for an a/b of the vtl 6.5 and the ref 3. perhaps this will be helpful since you own the ref 3 already. cheers, marc