I have a Rhumba 1.3+ (internally upgraded by Beckert) and this is not your father's tube amp. It is a fabulous preamp but in no way is it lush or romantic as you desire. I can't image that if you went further up the Beckert line they would fundamental change their character. Like you, I appreciate a balance control. You may want to expand your search.
Narrowing line stage search Conrad Johnson ET-6 SE VS. Backart Labs 1.4 Rhuma Extreme
Narrowing down my tube preamp search as follows:
1. Conrad Johnson-ET-6 SE: This line stage has no balance control and is not balanced. The retail price is $5900.00.
2. Backart Labs 1.4 Rhumba Extreme: Has a balance control and is fully balanced. The retail price is $8500.00
My preferences: Seeking a fully balanced system. My seating works best when I can control the balance as I do not sit in the "sweet spot". I am looking for an accurate but tube like sound that is lush romantic, especially in the midrange. Has anybody had the opportunity to compare these two line stages? Any advice with regard to which line stage might be preferable. Thank you. My entire system is listed in my prior thread entitled seeking a tubed preamplifier. My dealer who is truly excellent recommends these 2 line stages. Seeking some guidance as to the pros and cons of each.