Usually you run the pre either directly into the recording device, or into some outboard equipment (like compressor or eq) and then to the recorder. The output of each channel of the recording device can then be sent to a mixer for monitoring and setting up cue mixes. If you don't have individual track outputs on your card, then you may be forced to go to the mixer first. In which case, definitely use the line input.
Besides getting a cleaner signal path, the other advantage of having your mixer AFTER the recording device, is you are monitoring what is actually being recorded. If the tape/recorder is last in the chain, you will not be able to hear what is actually on the tape - and may miss some distortion or other bad stuff introduced by the mixer until it is too late.