Preamp connection to multiple powered subwoofers

I found the Artcessories Clean Box Pro to be a good line level buffer to run a pair of subwoofers in parallel with the main amps.  My preamp has two sets of outputs in SE and XLR configurations.  But that doesn't mean the preamp can drive both lines in parallel.  I confirmed this talking to ARC.  My preamp spec states a minimum impedance of 20 kOhms load.  My main amps have 22 kOhms impedance on their inputs and my Subs also have 22 kOhms impedance.  That means my preamp was seeing less than 11 kOhms total impedance.  That is too low and will affect the sound quality of the preamp as well as, I believe, affects the life of the tubes.  I found the Clean Box Pro which converts unbalanced to balanced or vice versa.  The SE (RCA) input side has 100 kOhm impedance and the output is balanced to my subs.  This was a perfect solution.  Now my preamp load totals 18 kOhms impedance.  Sound is much improved and the subs sound the same through the Clean Box Pro as when connected directly to my preamp.  It is possible to route the cables to the subs and then to the main amps but my current, already expensive cables are not long enough to reach the subs.  I would have had to replace all of my XLR cables to the main amps and subs.

@tonywinga I just wanted to say thank you! Your previous post was a game changer for me. I own a few different preamplifiers and power amplifiers, and noticed that the sound from my dual powered subwoofers seem to change and sounded inferior when I had one particular power amp in the system even though I have my dual powered subwoofers connected via low level connection to the preamp. I had been doing some research lately and started realizing that it might be some sort of an impedance issue, and perhaps my preamplifiers were struggling to drive the power amplifier. I checked the specs and found that this particular power amplifier has a 22k ohm input. It then occurred to me that perhaps the low level input on the subwoofers plate amplifiers might possibly be on the lower side as well. Did more research and landed on this thread here which seemed to confirm my suspicions. And then saw your recommendation for the Art Cleanbox Pro and so I ordered one from Amazon yesterday and received it today. Wow, I cannot believe the difference this thing has made. I have it connected to the set of pre-outs on my preamplifier and then from it to each of my subwoofers and the bass is absolutely fantastic. But in addition to this, I noticed as others have pointed out in this thread, that a struggling preamplifier can affect more than just the bass and so I am now hearing an improvement through the entire audio band, including hearing more detail, bigger sound stage, better imaging, and better separation and layering. I can’t get over how much of a difference this has made. Thanks again!