To my understanding:
1) DVD-Audio will not play correctly in 2 channels. You can get the front two channels of the mix, however, you'll be losing the rest of the music. DTS requires a digital connection to be played. Therefore, if you have an A/V receiver that will accept an optical or digitcal coax audio in, you can use it in 2-channels (make the receiver process it that way).
2) The two channel mix I know does not appear on all DVD-Audios, however, it may appear on some. I'm not sure. If it's just the two channels you're looking for, you shouldn't need to use the 5.1 in. Any analog in should do.