PREAMPLIFIER UPGRADE QUESTION

@bgross 

i doubt it. I was just answering for the OP desires for transparency and quiet. Maybe he could find a used one close to his price. 
 

happy listening 

@audphile1 My suggestion to be made, and now one that is given a substantiation by your own report, is to seek out Valve Exchanges that are recognised to work very well with the RC1 Schematic.

I have had a experience on a few occasions doing this, and the end result was remarkable.

A $1600 Amp + $400ish in Exchange Valves, might just convince the Amp is worthwhile staying on with and keep $7K in reserve. 

I had a Rogue RP-5 preamp that I loved and used a set of Mullard tubes in the line stage. I had it for 3 years until I went with a McIntosh based system.

I might suggest an old school cj preamp, I haven't heard their latest.  Very juicy, seductive and great sound stage.  Not neutral.

I've had both CJ and Bryston equipment. Both were excellent!

Bryston has exceptional build quality and clarity/transparency of sound, CJ sounds warm). I would prick my preference from these. 

As for the suggestion of Boulder, I would pick Bryston over Boulder... Which I did.