One other thing to watch with the 0404 USB is that the SPDIF outputs require you to use ASIO drivers. Lots of software, including RMAA, can't do this. This only matters, of course, if you are testing a DAC.
I use an 0202 with Visual Analyzer for various tests at home and at work. No doubt you can get something better, but it does a nice job for the money. You can run different programs for input and output, say the generator from Visual Analyzer and record with Audacity. Even though there's no explicit option for it, you can also play wav files and analyze them using Visual Analyzer.