Is there any standalone device that can play backup DVDs from a HD?

Yes, there are plenty. I bought the (now discontinued) RSH100 from these people some years ago to use in the car. At the time, that model was the only one that could decode DTS to analog (with an add-in card). The RSH300 seems to be an updated version of it.

For what it's worth, I can highly recommend the RSH100, at least for the stated use. I also seem to remember reading at the time that the picture quality on it was pretty good when watching on a proper screen.

If that's not enough to get you started, you could always have a look at this forum

Modded first gen Xbox does... and upscales at the same time.

- Josh

I bought this http://www.newegg.com/Product/Produc...82E16882994002 and it works fairly well although it only does 720P and I haven't tried that. For my purposes, it is perfect. I have a 500GB HDD in it and ripping most of my movies to .avi and @700MB size. Only real problems I have is I started ripping everything over into nero digital (mp4) and although it played fine, I could not fast forward /revers or use next to skip along hte movie. All the .avi's worked fine, hence why I am converting to avi. On a regular TV at most places I stay at when I deploy, hooked up via RCA, it looks as good as anything is going to look. You can put whatever IDE HDD you want.

Mvix also has an HD set-up http://www.newegg.com/Product/Produc...82E16882994003, but I made an HTPC. Although this Tvix http://www.tvix.co.kr/Eng/products/5100sh.aspx looks very interesting.

http://www.tvix.co.kr/Eng/products/5100sh.aspx

Flawless. Fabulous piece of electronics.....NTSC.....PAL...Composite to 1080p......

Having had a quick look at some of the suggestions made above, things are looking pretty good, except DTS decoding appears to still be a bit of an issue. Of course, most such boxes will have a digital-out that can pass DTS for decoding on a receiver but if the intended usage scenario is different, you've got a potential deal breaker on your hands, at least for me.

(It's not 100% clear that this forum is the best place for the discussion; the Portable A/V forum is probably better, even if the OP was not asking for portability.)