The preamp is just one link in the chain:
- player dynamics
- guitar (pickups, strings, wood, fret)
IIRC at that time he had Ibanez Musicians, IVP preamp, UE400 & UE405, IVP preamp, Gozilla poweramp, EV speakers
You can nail down all those and still not nail it cuz y'all are different people. Like Warren saying he sounded like shit playing through Jerry's rig.
IMO, the best preamp going these days is the Sarno SMS. Sure, most will say it's a Jerry preamp but at the end of the day it's a souped up Fender blackface preamp. From there mate up with a poweramp. Bobby has been big into the Mesas, go that route. For speakers EV, JBLs, Tone Tubbies. I think that's a much better route than an IVP and Godzilla.