I wasn't there for the Linda vocals but I did engineer and produce some other tracks for Christina on "Stripped". Her regular vocal chain is a 251 into a 1073 followed by an EAR 660. I recently used a Wunder Audio PEQ-1 in place of the 1073 and it was awesome on her. With someone like Christina there's no such thing as a "scratch", I always setup for what could be the "magic" take. On her debut record I used a Sony C-800G into a Brent Averill Neve 3405 followed by a DBX 165A.