I don't know what DAC's and processors the 1068 uses. The 990 is using one of Cirrus's newest DSP chips (the 49400), for what that's worth. The 1068 is a well-built unit, and while very few folks have even seen a 990 yet the impression I get is that it is on par with the 1068. Sadly, I think that it's just too soon to reach any conclusions that can be considered "definitive." Give us another month, by which point there will be a bunch of 990's in people's hands, and we'll be in a better position to say. Heck, I'll drag our VP over to the house at lunch one day (he owns a 1068 and 1075) and let him take a listen to it once I have mine settled in to the system.

Whether or not a stack of M200's (or a single 755) will make a difference compared to the Rotel amp depends at least in part on the speakers used. More efficient speakers may never need the extra 75W of power, while hungrier speakers (such as some of Polks bigger, low efficiency speakers) may benefit from it. Forum member wingnut recently bought an Outlaw 770 to drive a set of Polks because the 7100 didn't have enough power to completely satisfy them.

The USB port allows for stereo audio from a computer. The USB and RS-232 ports both can be used to install firmware updates.