I am slightly detouring this thread for selfish intent, as I doubt any answers to my query will benefit the OP. But, here goes anyway: Is there still merit in the old units such as the Heathkit XO-1 tubed crossovers? Assuming their operational condition is as should be, possibly with upgrades? When used with a basic tubed system, how may they fare compared to modern examples, such as a Marchand? My question is more than academic. Thanks in advance to any respondents, also those just giving it some thought :)