Cool, just riffing on my usual workflow. For clean stuiff I typically would start by modeling the actual original tube circuit in LTspice, then look at impedance scaling to an opamp circuit as appropriate. The only guitar AIAB tangent I've really worked so far outside of many Fender bassed ones was Dumble oriented, and all three I've built so far are radically different from each other. That's not necessarily such a bad thing though!
For my wants and needs Hiwatts have gotten my attention more as a bass thing, and in my case using a DR103 output transformer clone with 4 x EL-34 worked out really well for me.