If you plan to wash your quilt, I would prewash all the fabrics. Not only does this reduce the chance of shrinkage ( or worse, uneven shrinkage), it will also alert you to changes in the texture and finish of the fabrics as well as dye bleeding. These can be good or not so good, IKWIM, but at least you know before you spend a ton of time on a project.
I usually prewash using the same routine I plan to use later to clean the project. This includes both washing and drying. A lot of shrinkage occurs in the dryer. I find fabric finishes change when I use detergent to wash versus just rinsing. I appreciate this because pressing treated, unwashed fabric can give me a headache from all the chemicals.
HTH! Good luck with your project! Brocade sounds lovely for a quilt.