Rogue RP-7 vs. New RP-9 - What's the Difference?

I just got an RP-7 recently and I went to their site to look up the manual as I was setting it up and I see they now have an upgraded RP-9 model with different tubes (Russian 6H30P vs 12AU7 in the 7).  I can't seem to make out any other differences.

I thought this might warrant a discussion from those who know more than I do. Thoughts?
Chassis dimensions are identical for both, but that makes sense as they mention their "award winning RP-X hardware and software platform", which indicates to my mind that they are using the same base to work off of.

Audio Research's well received Ref 10 preamplifier utilizes (8) 6H30P's. The RP9 uses four.

Rogue msrp $7500 vs ARC msrp $33,000.

Looking forward to hearing the RP9! Always a great value product.
I had a chance to compare an RP7 to an ARC Ref 6, then I learned a little about the difference between the 6H30 and 12au7. The former is going to have higher transconductance - there’s supporting discussion on the technical side if you search it. I did feel that the Ref 6 resolved better, however in my system the RP7 sounded smoother in the highs - but not as resolving in the highs, and more fleshed out in the lower midrange and upper bass, but lacked the low bass power of the Ref 6 - the Ref 6, like the Ref 10 is much larger and packs beefier power supplies. Perhaps the Ref 6 was more accurate, but I preferred the RP7 overall. So if Rogue keeps the smooth character of the 7 in the probably more refined 9, it should be very competitive with more expensive options, but I wouldn’t expect the low end you get from the ARC models.
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I have and love the RP-5. I always thought the RP-7 was a balanced version of the RP-5 without the phono. I'm sure there was more to it than that. I'll be curious how the RP-9 compares to the RP-7 AND Rp-5.
Talked to Mark the owner of Rogue Audio. He said the RP-9 is build for the Russian 6H30P tubes with some different, more expensive parts. He did not quantify the improvement over RP-7. You could upgrade RP-7 to RP-9 for about $3K (with a different circuit board etc.). The real questions for me are (1) how much improvement over RP-7 and (2) how it compares with other pre-amps of similar prices (say $7K-10K). In my experience, may not be worthwhile to upgrade (e.g., I upgraded Schiit Yggy DAC to Analog 2 - but sold it at a loss when I compared the upgraded DAC to Metrum Adagio - the latter is much better).
Anyone hear the RP-9 yet?