SHayes

You could order direct from Superior Threads, their shipping is very reasonable and quick. Also I have have bought thread from SewThankful.com. The thread is a little cheaper per spool, some of my order was back ordered but those items were shipped later with no additional charge for postage on the additonal shipment. I love the Masterpiece threads for piecing and use King Tut in the top for quilting with Bottom Line in the bobbin. Good luck finding something that your machine likes.

plainpat

I bought Superior from mfgr site. Good ppl to deal with.I use the cones & now have a local dealer selling it.

StitchinJoy

I like A&E Signature cotton. It's made by the people who make Maxi Lock and it sews like Maxi Lock but is a bit stronger and comes in dozens of wonderful colors. I get it from Kingsmen Supply Company. The owner David Taft is a veteran with great customer service.
http://www.kmquiltingsupply.com/
No affiliation, just a satisfied customer.

candlequilter

I also use Signature thread and get mine from Kingsmen. I use Superior So Fine if I want a lighter weight thread that won't show as much. But Signature is a good thread that is reasonably priced.