First, I would consider a Ref 5se instead of a Ref 5. There is a big difference between the two. The Ref 5 is much closer to the Ref 3 then the Ref 5se. Even if it means having to wait a little while. The Ref 5se is worth it. I own one and it is magical. That is where I would start.
The Ref 210s are very similar to my Ref 110. They are very nice amps. But if it were me, I think I would consider a Ref 150. It can use either kt120 or kt150 tubes. And less tubes means less heat. The Ref 150 is optimized for kt120 not 6550 tubes and is a little better sounding amp. Unless you really feel you need the extra power.