Will be interested to hear what you pick up. I'm on the lookout for a new headunit to replace my RCD500. It's beyond rubbish, so I'm just weighing my options/bank balance.
Possibly an RNS310 as I don't want/need satnav. Just want something that will take an SD card, and allow me to see tracks/navigate folders, rather than the abomination that is the iPod "integration" I have at the moment.