I have an HQ Avante, and I've done 3 quilts with variegated top and bottom with no problems. I mostly use King Tut Thread. I have also used Coats and Clark, but probably won't buy it again.
Edited to say I use the TOWA gauge to adjust my bobbin thread tension, and try to use the needle recommended for the thread that I am using, according to the chart at Superior Threads.