ARC Ref-300 or 600 or 210: Which sounds best ?

Hi,
I currenty have an Oracle CD-Transport, a Jadis JS1 D/A converter, ARC Ref2 MkII Preamp, ARC VT150 Monos, Triangle Magellan Grand Concert and two Triangle Meteor 0.4 subwoofer.
I will upgrade the ARC Ref2 MkII preamp to a ARC Ref5.
Regarding the Monos I would like to know which one is SONICALLY best at low or medium gain levels: the old 300 or 600 or the new 210? I am well aware of the many differencies between these three models regarding age, max output level, power consumption, weight and size, number of tubes,...
In terms of price they are (as used equipment) somehow comparable (all three are in the 10-14k$ range for the pair).
But which one SOUNDS best??
I anyone has personal experience with two or three of these models in comparison I am thankful for sharing it.
Thanks a lot in advance!