And a basic answer to your question which hasn't directly been answered yet: YES. Image quality on Sony DSLRs will be directly comparable and essentially equal to that of Canon, Nikon, Pentax, and Olympus at the comparable level of camera.
All of the brands make cameras capable of near equal image quality - key differences come down to ergonomics, features, sometimes high ISO performance, lenses used, and photographer skill.
You will find Sony, Nikon, and Pentax have the closest performance similarities, since all three use the same sensors (made by Sony) in comparitive models. Canon has sensors of similar ability and quality at the same model equivalence. Olympus will basically equal the others in good lighting, and fall slightly behind as the ISO levels get higher, since they use a slightly smaller sensor not quite as capable in extreme low light situations.
Some models of every brand are better than other models - Sony, Nikon, Canon, Pentax etc have entry level cameras with less features and slightly lesser sensors, mid-level models with higher-spec sensors and better features, and all but Pentax have full-frame models with huge sensors for pro-level work.
Sony DSLR-A580 / Sony 18-250mm / Minolta 50mm F1.7 / Sigma 30mm F1.4 / Tamron 10-24mm / Tamron 150-600mm / Tamron 90mm F2.8 macro / Minolta 300mm F4 APO
Sony A6000 / 18-55mm F3.5-5.6 / 55-210mm F4-6.3 / 10-18mm F4 / 35mm F1.8 / 16mm F2.8 / via manual adapter, lots of Pentax K mount, Konica K/AR mount, and Leica M mount manual lenses