Here are some recommended wineries and wines from Barossa, Eden Valley and Clare Valley: [again, remember that many wineries source from different GIs]
Elderton - makes "elegant monsters" - the estate shiraz is a standout as is the "sticky" (dessert wine) semillon.
Peter Lehmann and St Hallett have impressed me in the past with their shiraz but it has been a while.
Torbreck wines get expensive fast and the Woodcutter's Shiraz is no bargain ($20+) but it manages that rare feat for Barossa, hedonism and restraint.
Henschke also can get very expensive but produces some impressive and mostly reasonable options as well. Try Henry's Seven from Eden Valley (a blend of shiraz, grenache, mourvedre and viognier). A note here - I find their whites delicious, nearly across the board, but generally conclude, as I often do in Australia, that I can get more bang for my buck elsewhere for white wine.
Hewitson makes intense reds with firm, but understated, structure, including the brilliant Miss Harry's (grenache, shiraz, etc.), Mad Hatter Shiraz and Old Garden Mourvedre. I want to like Ned & Henry's (shiraz and mourvedre) more than I do.
My experience with Thorn-Clarke wines has been positive but too brief for a full recommendation.
Sit down for this one. A wholehearted Aussie chardonnay recommendation, Heggies from Eden Valley. The wine shows restraint but lacks for nothing and even displays minerality and complexity I rarely find for reasonable prices.
Pewsey Vale Eden Valley Riesling shows what the area can do, plenty of rich, nearly creamy, citrus dominates with good acidity to back it up. Makes me want to eat sushi by the pool.
Pikes entry level riesling might be my favorite ever. The intense lime of the nose and palate can brighten any gloomy day and the subtle minerality makes me salivate for more.
If you like these two, or either one, step up and try a Jeffrey Grosset riesling, especially his Polish Hill (same region as Pikes). It's pricy but well worth it if you love riesling.
Jim Barry also makes a tasty Lodge Hill Riesling, although it is simpler than the ones listed above.
Finally, Mount Horrocks makes some delicious versions as well. The dessert wine, Cordon Cut Rielsing, offers wild concentration yet stays light on its feet. Their Watervalle Riesling (dry) offers a sleek, sexy take on rielsing. I burnt out on their shiraz years ago but remain fascinated with it. Girl Scout cookie season reminds me I should try it again...the vintage I overdid tasted like liquefied thin mints.