You would use the 2ch option in a case where you only have the R&L analog connections hooked up to the receiver. The thing about DVD-A though is, depending on the disc, they usually default to m/c even if you only have the player connected in stereo (its a disc thing, not a player thing), and you will only hear the R&L channels - the center, surrounds and sub will be missing (that's what would happen with my 2200). Some discs won't start playing until you have chosen stereo or surround, but many just start playing, and because the disc doesn't know what your setup is, it starts the m/c track. SACD is different - you can set it to select the 2ch or m/c track (if present) by default.
The main difference in the 2200's setup is that you will get an additional menu when you have selected the multichannel audio config, which allows you to adjust size, delay and levels within the player. I don't remember if you have that option for stereo.