Jon
Our astronomy club Sutherland Astronomical Society is holding a public open night this Saturday 26 March. The observatory is located at Green Point in the Sutherland Shire. More information can be obtained at
www.sasi.net.au.
Take your fiancee down there for a look. There will be Dobsonians in all sizes from 6" up to 14" and all forms of go to mounts that Ken mentioned. Some of these will blow your budget sky high but as Ken said it makes finding things all that bit easier particularly if your skies are light polluted like Sydney's are.
You can talk to the members about their equipment and you will meet some really nice people. I won't be there as I have other plans but it is well worth a look and there will also be talks on all things astronomy as well as the observatory being open for the general public to have a look through some really nice equipment.
Otherwise a trip to Bintel at Glebe will get you on the right track. Their products and service are first class. You do pay a little bit more than you would from others but the piece of mind that you will get what you are after is well worth it.
Wayne