Tube Rolling Advice for the Backert Labs Rhumba Extreme?

Tomorrow I have a Backert Labs Rhumba Extreme 1.2 being delivered, which has been upgraded by Backert to 1.3 specs. It will be driving the Luxman MQ-88uSE and the front end is a Qutest with M Scaler (Innuos Zen MK III server/streamer). Speakers are La Scala IIs, placed about 15' apart in the corners at a 45º angle. Soundstage is excellent and expansive with remarkable placement of instruments across the sound field.

If all goes well it will be replacing my L-509X, which is currently only being used as a preamp for the MQ-88uSE, so it’s being underserved in my system and will need to find a better home.

I am interested in any advice about tube rolling with the Backert Labs pres. With the Chord digital front end, I am getting a very layered, dimensional, detailed sound and thanks to the Qutest filters I’m able to adjust filters to best match the amplification. The MQ-88uSE has a gorgeous, full, warm sound and right now the 509X’s solid state pre is giving a nice sharp, detailed, and dynamic profile to sharpen up the tube sound a bit.

I don’t want a syrupy or bloated tube sound, more airy and detailed on the top with holographic imaging with solid heft on the bottom end. I’ve replaced the preamp tube in my Cronos Magnum II with a Cifte and was really happy with the impact on the sound.

The Backert comes stock with new Mullards, which I expect may have a slightly warmer sound than what I’m chasing.

Any advice?

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Thanks for the heads up @milpai  I will have to do some experimenting with that myself. 

I have swapped the stock Mullards for a matched pair of Mazda Cifte 12AU7, after being so impressed with the Cifte's in my Rogue CM2. I have found the Ciftes seem to really magnify everything the Rhumba Extreme does well - they are a good compliment to the airy top end, pinpoint accurate stereo field, and authoritative bottom end without changing the sonic character of the sound in any way. 

I will pull off the tube rings this weekend and see what kind of difference it makes. I'm curious to compare; the preamp is already using terracones, sitting on a butcher board, which is sitting on 3 IsoAcoustic Indigo Oreas so I wonder what difference the stabilizers are even making at this point. 
Would like to hear your experience after removing the rings.
Please do let me know. 
So I liked the sound without the O-rings for 2-3 days after which it started sounding fatiguing. I started looking into dampers that would not "constraint" my music. I came across Herbie's tube dampers. I was recommended the Ultrasonic SS tube dampers. I got them earlier this week and installed them right away. Well, I am pretty happy with how they got rid of the noise that I initially mistook as "open sound". The music and instruments sounds natural with these dampers. Love to get that musicality back in to my system.
Herbie's products are well designed and carefully implemented with materials that are musically friendly.  I have Herbie's Tenderfeet under every component in my system. SO musical.  Their decouplers are great for speakers and subwoofers.  With them in place the rest of the house isn't vibrating with the deep bass of many favorites...also the vibes aren't stressing the Tenderfeet.  Tuning a system is that last, best step in realizing a system's full potential.
NOS medical grade Amperex from Brent Jesse.Not cheap but wonderful sounding.