I own it, and its main advantage over the SDMX is that it has an SD slot, supporting upto 2GB additional flash memory. I own the 1Gb version, which can be upgraded to 3 GB total memory this way, and possibly even upto 5Gb once those Sandisk 4 gig flash cards become affordable. It comes with a digital FM tuner, and a carrying case and armband, making it perfect for working out also. I reviewed it in detail on Epinions. I know you didnt want any further additions to your list, but the Sansa is in my opinion, a better overall player than the SDMX. here's the review link:
http://www.epinions.com/content_186478988932