If you are using the 990's DAC, there should be effectively no difference between transports. If you get sufficiently "cheapo" you may run into some issues (really cheap stuff might not be able to operate reliably), but if you're talking about the difference between an entry-level player (the 1920, players like the Oppos or the inexpensive Pioneers, or similar inexpensive stuff) and a high-dollar player like the 2910 and beyond (all the way up to the Denon 5910), I'd expect two-channel CD's to sound the same when using the digital outputs.

There's been a bit of a buzz around the 'net today since Oppo announced their DV-970HD player. It's a $150 player with HDMI output (480i, 480p, 720p, and 1080i), 480p at the component video output (as well as 720p and 1080i for DVD's that aren't CSS-encoded), DVD-Audio, SACD, and some other assorted formats. It lacks the Oppo 971's Faroudja DCDi, but the initial feedback from beta testers suggests that it still packs a pretty solid punch on video. I'm planning to keep an eye on the player as a possible replacement for my Yamaha DVD-S1500.