As far as your requirement of 15 degree, machine washable, quick drying, etc. you are looking at either a synthetic insulation bag or one of the high end down bags with water resistant she'll and some of the newer quick drying down. I was in the same dilemma for years (guiding and camping in SE AK) and never really found the perfect bag. I have had Wiggys, Marmot, EMS, Kelty, MH, TNF and probably a few others. The main problem with synthetic bags is they are bulky and heavier but dry quickly and are warm when wet. Down has a lot of benefits but does not do worth a damn when wet and takes forever to dry. If money isn't a consideration look at one of the newer high end bags from Kuiu, MH, or Sierra Designs. There are so many options that it really ends up coming down to what functions are the most important to you and then narrowing it down through research.
Good luck, let us know what you decide on and how it works out for you.