Andy,
I used to run MSB Link DAC II w/ a 70$ dvd player and thought it sounded great, better in some ways than my Cambridge Audio D500SE cd player, which is a well-regarded budget player. I moved on and sold the MSB to a friend who has a much more modest system than mine and who also reported huge improvements when the MSB was inserted into his system. These dacs can be had used for around 150$. They automatically turn themselves on and off when they detect a signal, so your sis wouldn't ever have to fuss with it, and if she doesn't like it or notice an obvious improvement, you could always resell it for what you paid. Worth a try.
I used to run MSB Link DAC II w/ a 70$ dvd player and thought it sounded great, better in some ways than my Cambridge Audio D500SE cd player, which is a well-regarded budget player. I moved on and sold the MSB to a friend who has a much more modest system than mine and who also reported huge improvements when the MSB was inserted into his system. These dacs can be had used for around 150$. They automatically turn themselves on and off when they detect a signal, so your sis wouldn't ever have to fuss with it, and if she doesn't like it or notice an obvious improvement, you could always resell it for what you paid. Worth a try.