Wanted to point you to a place you may not have been to before. It's called Jazz @ Soutbridge and is on the Coffee Bean side of Boat Quay, on level 2. It's a classy place, good artists, and a generally nice place to spend a weekend evening. You can learn more about them on their website: http://www.southbridgejazz.com.sg/ I like the place and go there often.
M1 subscribers can also see the performance stage, live, on weekend evenings, by SMSing "cam jazz" to 8888 (you'll receive a live MMS back in a few seconds; video coming in end-October).