Sorry haven't been back in a while (and sorry for bumping such an old thread!) but I wanted to report that for a few months I was happily using the Soundcraft with RCA to my motherboard sound card, and had no noise issues whatsoever (listed as 104dB s/n, and I think it's pretty good, might even be that high, can't tell!)
The capacitors blew in the power supply on the mixer (maybe from having it powered on too long at a time? I was using it like 8-16 hours a day for 3 months) and it's under warranty, but while I'm sending it for repair, they said it could take a while.
So I found on amazon a new Focusrite Scarlett 2i2 for 135 and then 15% off. 114 for a bus powered little box with pretty good pre's, I won't complain!
You were all correct about me stressing too much - get whatever feels right at the time, and move on later. I guess I'm one of those "learn the hard way" type of guys, so I need experience. It's working out.
Something is a bit noisy now and then, but I can't tell if it's the pre's or the mic's that I'm using... (GLS ES-57, AT2020 that i might replace, and a EV PL84) the EV is silent practically up to like 8 or 9, but the GLS (of course its a cheap dynamic) has quite a floor, and the AT2020 is noisier than I want a condenser to be... Defective? perhaps... Too sensitive and picking up noise that I can't hear in my room? maybe...
Any thoughts on this?