A long-time Memphis architecture firm plans to build a new headquarters and apartments in the South Main neighborhood of Downtown Memphis. Archimania hopes to build a 5,000-square-foot office building, a 20-space surface parking lot and a six-unit apartment building on half an acre at 705 S. Main St., southeast of the intersection of Main and East Carolina Avenue, for $1.7 million. The firm's principals, Barry Yoakum and Todd Walker, acting as Filament LLC, are scheduled Nov. 11 to ask for a six-year,…