I use PC audio in my two systems, one with a wireless SB3 and one with a USB device but both from the same laptop and both using a NOS DAC via SPDIF. The determinate was physical proximity not cost or sound quality. If you are concerned w/ the PC being an annoyance because of its noise or the RFI, EMI it will generate then the SB may make more sense.
My personal experience, leads me to believe that the USB path, w/o the additional translation to SPDIF, i.e. using I2S directly to the DAC chip has an edge in ultimate resolution, but very high quality playback can be achieved with either architecture. There is a whole range of options in the USB method that utilize I2S. John Swenson over on the Asylum has found a way to access I2S on the Squeeze Box however I don't think thats ready for prime time yet, but I keep cautioning that the rate of change may make everything very last year overnite
Slimserver is criticized by many but I think it works well and I find it more convenient than Foobar and yes you can use a browser interface from another PC on your home LAN to access it as opposed to Foobar which requires a remote control session for me. The debate over whether or not to continue using a CDP as opposed to PC audio is simply settled for me. Like MFSOA, I have multiple sources in both systems and I also like the things that a tubed preamp does to the sound but I wanted to try both architectures and I'm satisfied with both.
BTW, you can do internet radio w/ Foobar too, its just that I find the (bit rate,compression) sound quality total crap.