Thanks for all the recommendations. Though The new Okura looks nice, but it's almost as expensive as Aman, and out of budget.
I've never stayed at an old-school Japanese hotel chain before, so I may go with Imperial, but will read reviews first. Looking at Andaz & Shangri-La I don't think they fit my tastes that well. I think PH or MO, and I don't want to rule out FS yet but it does not look like it's got enough amenities (eg no pool).
I like the Imperial but would not consider it a luxury property by any means. And I still love the PH but if you're looking for a convenient location, it is not a great option.