In an anomalous perk, the high end hotels in Adelaide usually offer weekend package deals, meaning that rooms are cheaper than during the week. This brings the prices closer to the more moderately priced hotels that offer more consistent rates.
If you'd prefer to stay away from the clamour of town, North Adelaide could be the option for you, offering a leafy tranquillity in which you can situate yourself. Perhaps it will be from here that you organise your wine tour to sample the local Shiraz or Riesling.
Alternatively, Glenelg is a beachside town that offers a number of hotels from where you can foray into the local surf culture. It is a popular tourist destination thanks to its more relaxed nature and hospitality choices, while still being located fairly close to Adelaide city centre.