Looking to replace my eclipse 8445. My main concern is SQ and I do want something that will play my ipod but I don't need anything else like blue tooth. Would like to stay under $500
There is a great search engine that you can narrow down head units by vehicle, size, options, and cost. The main attributes I look for in a HU are pre-out Voltage of 4v or more, FM Sensitivity (the higher the dB, the better), CD Signal to Noise Ratio (the higher the better), and the amount of pre-amp outputs. You can usually find better prices on Ebay, but some of Crutchfield's specials are hard to beat and are much cheaper...
These days it is hard to find a HU that is 100% dedicated to SQ, but you really can't go wrong with Alpine, Pioneer, Clarion, Eclipse, Kenwood Excelons, and JVC Exad all make fairly descent HUs.