knit-in,
I'm one of the folks with the wonderful priceline-amsterdam deals. Read Sheryl's board and use the link to the priceline.uk board for more info---and you'll see that you do have a choice in hotel type when placing your bid.
I believe the two Marriott's are both at the highest priceline level and every hotel booking website I've seen refer to them as "5-star european" That would likely compute to 4-star US...in other words, you don't have to worry about the rooms or the bathrooms.