The PSA P300 is a favorite of mine, though it has limitations. The idea that a regenerator can reproduce the expected AC wave form is essential. Currently, an engineer and I (mostly him) are working together on a higher performance P300. I cannot give too many specific details, but in general capacitance has been increased, and output transistors in the P300 amp have been replaced. Getting NOS parts for some other issues make it slow going. Still though, those damned transformers get too hot! Might have to rethink that as well.
In the end, I like the concept of balanced power, and have been using a BPT product for many years. Each secondary (6 in all) have separate windings, allowing different components to have their own circuit. Between that and the balanced concept, I am happy. Power amps do not run off of this unit, but use a grays power 400S in parallel with the AC input. Again this a good idea for me.