If you search the model of an audio interface like "konnekt 6" + "rightmark" in google, data pages will be in the results. They usually are titled Right Mark Audio Analyzer or something and may be foreign like this. You may not be able to read the page, but with google translate you'll be able to decipher it. What is interesting is that tests generated from this program are published all over the web. Chances are you can use this data to compare different audio interfaces. Things that matter like THD % spec (lower is better) and crosstalk graph give a good idea of audio quality. Items like dynamic range have DB values where higher is better. If you see the frequency response fall off too early, maybe avoid that interface!
Search for some cheaper or older firewire models. It is pretty amazing. M-audio does make interfaces with very good spec. Motu's entire line also is very good. TC Electronic is very good. You may not need to spend $1000 to get a good signal.