For really good thread, get bonded nylon. It comes in many sizes. If you want to sew a bombproof pack to carry hundreds of pounds, use size 92 like Mchale. But, you need an industrial machine for thread that large. Size 69 is the largest with a home machine.
But, for a quilt, you do not need that much strength. The polyester thread at Joanns or Walmart is perfect, and the price is right, and shipping is pretty fast if you go there and pick it up yourself. If you want to see some really confused faces, go to a sewing store and ask for Bonded Nylon Thread. Everyone I went to looked at me like there was a hole in my head.