Yeah, the Wheatfield is great. I remember fondly listening to Fred's Wheatfield with $1K of tubes in it at Ray's house.
Then again, my K340's weren't balanced at that time. I'd have to say [from memory] that the K340's balanced is a whole 'nother story. Sort of like the change that happens in the Senns when you balance them.
I think that if Mikhail had a better source and the tubes weren't chosen specifically for his R10's it might have been a different story though. But in a way I am sort of glad. It is bad enough I am lusting after the Balanced Max. I can't afford it right now... and I DEFINATELY can't afford the SDS-XLR.