Thanks Febs.
I found the shareware software LP Recorder, which worked quite well. Unfortunately I could not avoid a static background noise from my harddrive, audible in both files. Also, the above mentioned hiss of the Apple-FW unfortunately seems not to be audible on these files, though I used a splitter and hooked my super.fi's on during the recording. All other settings where as flat as they could be, No EQ, No Gain, No Nothing...so, let's hear, if you can spot an audio-relevant difference between these recordings.
Here are the two files, compressed to FLAC, and each is about 5MB.