Backert Labs Rhumba preamp

I am thinking of going to an active line stage for sometime now. I have a separate thread for that and people have suggested some good choices. The reason for this thread if that, while I have all along said that  don't want tubes in the system, a few have convinced me that I should try tubes in the system, especially with ProAcs.
With that said, I researched a few tube preamps, that have XLR out and the Backert Labs Rhumba is the one that has only 2 tubes, which makes me comfortable to "deal in tubes".

I would like to hear from Backert Labs Rhumba owners who moved from Solid State preamplification to this preamp. What are the differences you heard? Any improvements?

I read a review on the Stevehoffman forum and the user mentioned that there is a "hum" in this preamp. This bothers me and hence I decided to check on this forum, if anyone has experienced this with the Rhumba in their system. One poster on this forum also confirmed the "hiss":

So I was wondering, if there are any users who have recently purchased this preamp and what is their experience with the hum/hiss issue.

BTW, I blame Ralph of Atma-Sphere, Almarg  and my dealer for making me consider tube amps :-) Can't believe I am creating this thread.

@jwpstayman , thanks for pointing that. But I managed to talk to Andy at Backert Labs and he answered all my questions. Looks like the new Rhumbas do not do phase inversion issue, since a transformer that they use inside does it (not sure if I put it the right way, as Andy explained).

I am impressed how much time Andy took to answer my specific questions related to hum, phase inversions, tube life, volume control, etc. Andy also told mentioned about a very good upgrade path for existing users. Besides the Parasound JC2 and Jeff Rowland Capri S2, I think I will seriously consider the Rhumba as a preamp upgrade. Frankly this is probably my number one preference for now.
The MP3 may be really good, but is currently out of my price range and also comfort (no. of tubes) range.
@milpai The Rhumba is a line stage. If you get the MP-3 as a line stage, it only has 4 tubes. The remaining tubes you are probably thinking about are for the optional phono section. The MP-3 has a polarity inversion switch.

Since I know Andy really well, and sorta know Ralph as a former customer, I won't go on in any detail here, but wanted to point out that it's pretty cool that both the Backert & Atma-Sphere gear is voiced by performing (in Andy's case -- professional) musicians. That may not matter to you, but I think it's cool and perhaps relevant. Cheers,
@sbank Thanks- I often wonder what people mean when they use the word 'voice' in that manner. I've often interpreted as some sort of tonality? - but it could mean something else. FWIW we don't do anything to compensate our circuits for bandwidth, and while we do listen to the gear of course, we don't do that until we've optimized for least distortion and maximum headroom.

From what
@sbank ,Thank You for the reference. It does help to know this detail because reviewers have a different expectations than designers.