Hi Carlos,
At night in Sydney I don't think you need ISO1000 - this one was handheld from a ferry:
http://www.dpreview.com/galleries/73...44527/p1020278
If you're using a tripod and the subject is static you can use ISO100 and longer exposures even at night. An extreme example of mine - note this was taken in MOONLIGHT at ISO 100:
http://www.dpreview.com/galleries/73...k-by-moonlight
These were from a small-sensor compact and you can see the exposure details; if you are using a DSLR the noise (grain) should be a lot less than you can see in these.