Music Reference RM-200

Yes, the first version of the Music Reference RM-200 was reviewed in Stereophile’s April 2002 issue and rated "A"(tubes). I owned the amp for several years and saved the magazine. It excelled even more with upgraded KT-88 tubes. A very solid performer, but I have since sold it and down sized to solid state integrate.
I'm not sure about subbing the 6BQ7.  I would get in touch with tubeaudiostore.com and pose the question to them.

The original can be sent in and brought up to Mk.2 status in every way except for the capacitor forming capability.

No it can't. I was never aware of the upgrade, Roger never speaks of it these days, and if they were done in the past they aren't going to be done any longer. We will continue to service RM-200s.

The 6BQ7A supplied by the Tube Audio Store are the correct driver tubes as they need to be aligned for offset which Roger does (and I will soon be doing) by hand. As for the output tubes, RAM KT-88 are stock, most folks like the Gold Lion KT-88, and my personal favorite is the GE 6550. Some people run KT-120, good luck with that.

Thanks for the help and clarification. I thought both versions were rated class A. This other person thinks that it's only the mk2 version and he thinks I'm intentionally misleading. I'm sure they sound different but that doesn't mean they both are not great amps. Some times designers change the model for a different audience who uses different kinds of speakers or that they just want to try something new and experiment. At first, I did not like the mk1 model but then I spent more time with it and realized how good it was with the tone and timbre of instruments, as well as the balance of other qualities throughout the frequency spectrum. I wish it did have a little more damped bass, but everything has tradeoffs. I will call Ram Labs about the tube swap because I know that they are used in these amps in unique ways. 

Does anyone have suggestions for a good balanced tube preamp?  

I've used an Atma-Sphere MP-3 with the RM-200. Both units are fully differential from input to output which is an added benefit. I really don't know of another preamp that is fully balanced like the MP-3 but others might have recommendations there. However, there are plenty that offer balanced outputs which is not quite the same.

As for the tube swap I'm trying to save you that phone call because you'll be speaking to me. RAM 6BQ7A hand tested by Roger. You can play with other 6BQ7A or their "equivalents" at your own risk. Good luck trying to get those output tubes to balance. The driver and output are tied together so the offset of the driver tubes is critical.

The damping of the RM-200 is 10. That puts the output impedance at just under 1 ohm. The nice thing about Roger's amps is they respond well to light loading, which he recommends whenever possible. Meaning if you have an 8 ohm speaker use the 4 ohm tap, a 4 ohm speaker use the 2 ohm tap. Less distortion, more efficient operation, and you get more damping.

There's also an RM9 MK2 listed by TMR with vintage Siemens EL34 tubes for $2,499 (can probably negotiate down to $2,250).  I have the RM9 MK2 and have success with both RAM EL34's and GL KT88's.  Great amp and a great value!   I've owned many tube amps, some that retailed as high as $18K, but the RM9 MK2 is as good as any tube amp I've owned.

That $1500 price for the RM200 caught my eye.   If I were in the market for a tube amp I'd snap it up in a heartbeat!