If you already have thread that you think will look good on your quilt ... make a test sandwich with the same fabric and batting that you will use and play with that thread. I always make a test sandwich before I begin quilting any item - I want to make sure that all components will play nice, that the thread color will look nice, and if there is a new quilting motif I will be using I practice that as well.
When quilting, you can determine if the quilting will be very visible, or almost invisible by the weight of the thread you want to use. I've quilted with a 12wt when I wanted the quilting to be the star, and I've quilted with a very light 50wt combined with 60wt on the back and you have to look very close to see the quilting.
It's all up to you