I was looking at the CD-less Alpines. The marine model matches well but is very pricey. I went with the JVC KD-S100 which was $129 delivered from Crutchfied. It has an SD slot in the head unit, can use the iPod adapter, has an aux in on the back and a USB in the front. It can read a flash drive via the USB. Not sure about the HD radio. Does have a redundant CD player which I dont use either.

You could use a thumb drive that reads CF cards to utilize the USB. I am using one to read SD cards bigger than the 512MB that the internal slot supports. I also have a micro SD reader that lets me use micro SD cards like my phone uses. They are cheap and plentiful. Here are links:

JVC KD-S100 CD receiver at Crutchfield.com

Newegg.com - Kingston FCR-MRB 1 card USB 2.0 MicroSD Reader - Card Readers