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?

128x128Ag insider logo xs@2xjsqt
My faves for my Backert.... a pair of CBS 5814a. Just a well balanced sound across the range, but with a lively presentation. I tried a bunch of 12au7s, but always come back to these!
Thanks - I'll be checking those out too.

What Backert do you have? What does the rest of your system look like? Thanks!
I have the Rhumba 1.2, with upgraded output caps (a pair of Audyn True Copper Max), and an upgraded SR Blue fuse.  Great preamp; responds very well to tube rolling!

Check my system here on Audiogon... a lot easier than trying to describe. Pics are outdated, but the equipment listing is current.
@1markr wow, that is some impressive gear, I bet it sounds awesome. 

I just got my FedEx alert that the preamp has delivered at home... now just 8 more hours until I can get home and start working with it!

What difference did you notice with the SR Blue fuse? Have you found an improvement with an upgraded power cable? 

Thanks @jsqt!

Christmas in August! Love it! Have fun with your new toy!

Adding the SR Blue fuse was like a power cord upgrade from stock. Sounds cleaner, a little more open, a little more detail, but not because of  added brightness. Not a massive difference, but IMO worth the cost of upgrade.  The Rhumba definitely responds to power cords, but interestingly enough, it likes my homemade Oyaide power cord I made vs. more expensive ones I have from Audience, Verastarr, and others... 
The Backert is getting its first workout tonight. I'm not ready to make any gushing endorsements just yet but I am very impressed, particularly with the imaging and separation. I've noticed it's a little "soft" sounding - not syrupy or bloated or muffled, just a little polite, particularly on the bottom end. I suspect it may be the Mullards.