Regarding the aperture...larger aperture is usually a good thing, but in the inner west of Sydney I'm not convinced you'd see much difference
however, at a dark site the difference would be more noticeable on the fainter objects. Whether it is worth the extra $200 is something only you can decide.
But keep your eye out in the Star parties section as a group of us regularly meet up around New Moon in the Blue Mountains, and there are other meets in and around the Sydney area. Depending on who/what scopes are present, you may be able to try before you buy...