Hi Aidan,
I would go with the 10" Skywatcher, good bang for your buck.
With a 10" on the EQ6, you should get some good shots with the DSLR.
I have an 8" on an HEQ5 Pro and shoot from Kellyville Ridge which has some horrendous light pollution from Blacktown, Parramatta and Parklea.
Here is a link to some of my photos, most of which were with an Atik 314L+ through the 8" but some were with a Canon 1000D (standard).
It is possible to get galaxies in Sydney, you just need LOTS of exposures and good light pollution filters, I use a EOS Clip CLS filter in the Canon to remove a lot of the sludge, although you have to white balance it first as it makes everything go a bit blue which is tricky to rebalance later.
One reason the aforementioned Hutech IDAS-LP is better, as it keeps a natural tone to the photos and is all round I think a better filter.
Give it a bash, the 10" F5 will be more forgiving and easier to get started with.
Cheers
Chris