There are people here doing what you describe already; consider it a path to take. I can't point to a specific thread, but if you search various 500 threads you'll probably find it.
Yup, I read and search a lot. I'm just pointing out a product that enables converting any number of active projects like SSL 9k preamps (which in pure form require two separate bipolar voltages) to 900 series using the board I posted about.
As well, this PCB card would enable a lot of projects to go unmodified to 500 series.
I'm just glad I don't have to get out my etching supplies and steal my wife's hot plate!
CC