The Westin stands out as a good redemption at 30k. It is one of the newer properties on the list. You get the lounge and the downtown location along with the upgrades.
With the new MRT station and its proximity to the Robertson Quay area, the 4P is worth considering for 20k a night as well except the rooms are tired and elites only get a welcome drink.
Please note the RC Singapore does not participate in the Bonvoy programme. You will not get a complimentary upgrade or lounge access here.