Urban legend that CS-800 is the same amp as BGW-750B, i used to believe this too, but have been more accurately corrected. Electronically, the CS 800 is probably the closest to the original 750. The 750 was revised many times with the later E, G and H versions offering significantly more power as well as pretty much totally redesigned circuitry.
FWIW, and IMO, they're both truly "great ones" in the history of amplifiers.
There is a legitimate connection and similarities, but too few to call them "same". There were no lawsuits after all.
It seems the reality is that the BGW 750, and original series CS-800 chassis sheet metal and heat sinks were sourced from the same vendors, and possibly even some design "sharing" went on, but most likely it was all about economics.
I have a BGW 1000, the first BGW product, and the amp that started it all where BGW is concerned. From a few years of casual research i have learned that the original engineer of the RCA transistors used in the 1000, was also the designer of the BGW 1000 and probably the original 750, 500, and 250 models. AFAIK, this is just one person. originally an engineer from RCA, and possibly also a close friend of Brian G Wachner's. Too bad Mr Wachner isn't still with us and able to shed more factual light.