I'd recommend at least a little caution or careful planning before deciding which lossless format to rip to. The one drawback to using iTunes to produce lossless files is that playback of AAC lossless files is not widely supported - you can play them in iTunes, on your iPod, and through an AppleTV appliance, but everything else will be hit and miss. Likewise, FLAC is not supported by all players.

When using USB to the 990 or the 2150, the sound card isn't in the signal path. The 990 actually acts as a giant USB sound card.