IMHO 20metres on a Powermax is going to be hard work without a booster. If you use a booster, you would place it, at the most, 25 ft. from the wand, so you wouldn't want the hose in one piece. Solution supply would suffer at that distance too with the small pump on a Powermax, even more so if running upstairs.
And don't go for the cheapest hose, it's KRAP, go for a good quality smooth bore.
Safe and happy cleaning
Ken