I use a Empirical Audio Off-Ramp with a EA turbo-modded Dack!. Prior to that I had a Modwright tube modified 999es. I wouldn't trade this set up for any CD player. As for the SB, I've never used it. It's a little less expensive when modified, but I'd be shocked if it had a more dynamic presentation than my EA components. I'd be more than happy to let someone come over for an a/b.

For the money, either choice would bring you SQ hard to match with any stand alone CDP.
Yes, you can play streaming audio with this setup--at least my EA stuff, not sure about the SB.
You rip the files from your cds to your hard drive. Then you use something like foobar to play the files off your hard drive, eliminating the need for the CD--one of the major advantages of computer audio. There are many posts on this topic.
How far are your speakers for your main computer? You can run a decent length USB cable from one to the other.