If you are worried about breakfast, at least in the past, I usually got an offer of 50% off for breakfast when I didn't have it included. Alternatively they offer some dining packages that provide some savings if you plan to eat at the hotel a lot.

The Singaraja rooms have a bit different décor (darker) than the Classic rooms and are all in the Central Wing (4xxx). Are they nicer? Well that depends on personal taste. The offerings from the Singaraja "lounge" are negligible so in the end it comes down to whether you like the room design or not (look at pics).

BTW, 20$ is the normal difference between Classic & Singaraja room so not a super special deal or anything like that and don't forget the 21% (10% service + 11% tax) on top for everything.

YMMV