There's a few things to remember here when comparing CDP to PC/DAC combo...
It's not all about how you -play- things but it's also how you -read- them.
Yes, you can rip your whole CD collection have it on FLAC and then replay it. I for one am of the opinion (and I might be wrong here) the quality depends on a great many factors.
1. Quality of your CD/DVD-ROM in readying the data.
2. Your Rip software/Encoding software.
3. The format/quality of which your saving your stuff in.
Another thing to remember is that CD's were not designed to be read in and converted to digital formats (ie.: flac, ogg, mp3), it just happens that a means was made available to do so.
When CD's were encoded they were/are designed for CD players.
Another thing you have to remember is that a CDP is designed for one thing, playing CD's, and that's it's dedicated function, they have technology to correctly read and transmit the information from the CD to the output plugs/devices. Depending on the quality of the CDP it get's better or worse...
The difference between PC + DAC vs. CDP is enormous if we do a pound per pound comparison.
In some circumstances, it is better to have a CDP + DAC, because some CDP are better transports then players (I remember cyrus has such combinations).
Going back to your original question, I would say without a shadow of a doubt that a good CDP (or a crappy CDP transport + DAC) would always beat a PC + DAC combination, IMO. And I say this through experience...
I have both situations setup at the moment in my room, and the CDP always produces more then the PC/DAC does (quality wise that is).
Anyway,
my 10p,
J