Have you called Robert @ ValueElectronics.com (banner above)? If not there Crutchfield sells them too, just call and ask them as well. Only the people that can actually see or touch the inventory will know.
From 1994 - 2003 every manufacturer designed their own DIRECTV receivers from the ground up. But when News Corp took over their vision was a standard user interface and remote control for every box, so customers and their CSR could more easily support the products.
So LG, Philips, Samsung, Thomson and Humax all build the same box to DIRECTV's specifications. 100=RCA/Thompson 200=Samsung 300=Phillips 400=Hughes 500=Humax 600=LG so your H-20-600 would be mfg. by LG.
Called Value and all they have are 600s. Has anyone been able to get an H20-100 that didn't come directly from DirecTv? I called "Advanced Technical Support" about getting a replacement and they said they couldn't guarantee I would even get an H20! I asked them what other receiver does MPEG4 and they said, "Well, since you already have that we probably would replace it with another H20 but we can't be sure which manufacturer it will be." ARGGGHH!
Lynskyn, Sometimes I wish I had a -600 again. Like every time I want to watch CBS-HD over the air and can't, because the tuner in my -100 doesn't deal with weak signals as well as my -600 did. But whenever I'm trying to find something in the guide, I'm glad I have a -100. Why can't one of these STB mfgs get it right?