As always, you have to look at this objectively and pick the HU that has the features you want for the price you want to pay. If you pay 400-500 you are going to get a good HU, regardless of the brand.
IMO, the best HU on the market is the Sony CDX-C90. It has the best internal electronics of any HU on the market, bar none. There are other HU that are wonderful also. Nakamichi decks don't have a lot of features but have high build quality. Companies like sony and Pioneer are ALWAYS going to get mixed reviews because they have a broad product line from sub $100 models to HU upwards of 800.00. What will happen is people think that they should be made with the same quality which is unrealistic. They have a problem and call it worse than audiovox or sparkomatic.
Clarion, seems to have the best quality from top to bottom in the HU they offer. Alpine, Eclipse, and Nak could easily be the same or better quality but the difference between all of them is negligible to say the least.
