Those 2 premiers have the same internals, so I doubt that you will hear any difference between them. They are too bright sounding units for me. I'd go with $100 Clarion DXZ665MP. It has the same internals as Clarions' $500 DXZ955MC but no DVD playback, no color screen, no 5.1 preamp outputs, no software for time alignment and a bunch of practically useless digital sound enhancements. Both of them have VERY natural and dynamic sound.
http://www.clarion.com/us/en/products/2006/audio/source_units/cd/DXZ665MP/us-en-product-pf_1134643389110.html
http://www.clarion.com/us/en/products/2006/audio/source_units/cd/DXZ665MP/us-en-product-pf_1134643389110.html