Sequel to 'Witcharia' (1977)?????

Don't you mean Suspiria (1977)? If that's the case, than it's a totally stand-alone film.

The theater is like a faithful wife. The film is the great adventure, the costly, exacting mistress

The connection between the two films is that both were Italian horror productions under the supervision of Joe D'amato that were filmed in Massachusetts in 1987 and 1988. The films are more logistically related than sharing common plot elements aside from being set in creepy old abandoned houses. The casts are primarily Americans but the production teams were Italians, with the exception of Laura Wendell in GHOSTHOUSE who is a popular name from Italian exploitation films. They were both more or less aimed at teen markets, with this one perhaps having a bit more of a grown-up flavor to it, including nudity and sexual situations.

I think they are both fine movies for what they are worth, I too prefer GHOSTHOUSE but WITCHCRAFT has some impressively tasteless stuff in it too. I think a lot of people get distracted by how David Hasslehoff and Linda Blair are both in the cast and disregard what the film has to offer. It has a certain quality to it that's very cheap & tacky, yet there are some memorable sequences and a mean spiritedness to the proceedings that is quite cruel.