For sure my replay comes late, but I had to write because I used exactly the same gear than you. And now, since five days I own a Malvalve Headamp.
Today I cleaned up my rack from the Cavalli Liquid Fire, a modified SRM 007 and a HighAmp Hybrid.
Was it worth to buy the Malvalve? For sure! I couldn't expect an Amp being better than the Cavalli, but the Malvalve is a step further. It's sound is stronger and cleaner, there is even more control. Maybe Cavalli's stage is deeper, the Malvalve's wider.
Could be the Cavalli equals the Malvalve with an unbalanced source. My Ayre QB 9 DSD prefers balanced outputs. Not knowing the big Woos the Cavalli IMO is better than anything else I have heard for dynamic headphones.
Now to the electrostatic part. I still have a Stax SRM 007 which is modified for 6S4A tubes which is a great thing!!! And also the HighAmp Hybrid ( a DIY project by Rille) is known to beat all the Stax amps, but both will go. The Malvalve is strong enough to drive the SR007MK1, to give him a powerfull, detailled bass. Wonderfull combination!!!
Some things I don't like on Malvalve: the outputs on the back ( even you can leave one dynamic and one Stax at the same time and switch with the mode bottom). The small buttoms and the little display. But sound will let you forget about thoose things!!!
Now I have to sell a lot of amps and cables and have got a lot of space for new headphones...
Let me know about your decision. Did you get a Malvalve?