my experience in replacing caps in BGW amps
I replaced the two electrolytic caps in each of the amp modules in my 13 BGW 250D or 250E amps, and got better bass response . that meant 4 electrolytic caps per amp>>there were two caps in channel 1 and two caps in channel 2. I have not done this yet to my 750B's; but wouldn't be squeamish after my first experience.
They were all in the signal path; and really wasn't too expensive (3.00 /channel). Just remember there is a + and - on electrolytic caps.
I didn't replace the two much larger caps in the center of the amps...as an FYI. Pretty easy to do, just use a good electronics grade silver-tin eutectic solder, and while you're at it reflow any suspicious solder joints while you're in there.
Oh and invest in a good soldering station, I got an industrial station for ~ 75.00 in great shape off eBay.