i buy all of my thread from Connecting Threads- have had great luck with all of them, good prices, good color selection- good weight/type selection.
i have a viking sewing machine that will not accept alot of threads- like some coats & clark-- but it also does not like some others- it is aggrivating to spend money on thread to only find it will not work in your machine- when that happens to me i save it for hand work- or as a basting thread.