It is not recommended that you switch topology types as many of those changes are in notch filters and B&O likely had different drivers or a different batch that needed compensation. As far as parts quality, since all bands are in parallel and there are a lot of parts, I would focus on replacing any electrolytics in the mid and tweeter circuits with poly caps as it does not appear there are any iron-core inductors in there. Check out either the Dayton or Fast PA Series from Solen. I have had excellent results with these.
