What is your definition of mid range?
I agree, the Rocks/Circular Quay is the ideal location, but you will generally pay more pay more there than further back into the city (CBD) or Darling harbour etc. Hotels such as Sydney Harbour Marriott, Intercontinental & Sir Stamford fall into my definition of mid range for that area. B & B Sydney Harbour often gets recommended.
Back a couple of blocks is Travelodge Wynyard.
It will also depend on your dates (saturday nights usually more expensive).
Have a play around with your dates on www.hotelscombined.com.au/City/Sydney.htm gets the best on-line prices from all the sites.
That's really helpful - thank you Mia!
www.wotif.com.au is a good resource, too.
Thanks for your input, everybody! We're sorted now and very much looking forward to April - and very grateful for all your help :-)
Out of curiosity, where did you end up booking? Was it an on-line deal or with the hotel direct?
The post about bed and breakfasts got us thinking about stuff other than hotels and we're going to give Jeffreys St B&B a try - booked direct with them :-)
Thanks, enjoy your visit :)
Don't forget to tell us what it's like in your Trip Report please !