There is a frontal port loader that JVC makes. Seen it at Curcuit City a few weeks ago. Probably the best bang for your buck, as it was priced at about $200.
I have seen ads for Pioneer and Alpine units with a firewire port, but I can't recall where. Perhaps Crutchfield. *shrug* A little searching on the web and you should be able to find something. I would prefer firewire over an SPDF connection anyday anyways.