FWIW, I also tested many cheap chinese $2 eBay sound "dongles" and many of them only had a mono single channel audio input (you need stereo input for IQ SDRs like the softrock).
The cheapest USB sound card that I eventually settled on with stereo Line input, was this one:
keywords "usb sound card 5.1"
It works fine, but it maxes out at 48kHz. It seems to have a slight audio IQ balance problem when switching between bands, though that could be something else I haven't pinned down yet. TBH the balance problem is probably me being nit picking perfectionist. I haven't checked but I'm guessing any transmit harmonics are low enough to be snuffed out by the output filter.
