With regards to the XLR method, keep the phantom power off, keep the pre-amp off (or zero), and just use the faders on that channel to adjust levels. Many mixers also have balanced 1/4" plugs that you can use also.
I guess you could go from the PSA to the soundcard directly...never tried that. You'd still have to get some type of cable converter. If you go from both of the PSA 1/4" outs to a single stereo 1/8" plug (for your sound card). Although, I'm not sure if there will be impedance problems or not...? The PSA has a +/- 10db switch on the out...that may cure that problem.
If you run it thru the mixer, it might make things easier. That way, you won't need to keep plugging and un-plugging stuff from your soundcard. Just setup the mixer to do that, and now everything is easily accessible.