Mic-pre to computer

A mic pre raises the microscopic electrical output of a mic to line level.  So it is best practice to connect it to a line level input, such as your 3/4.
 
However, many interfaces only have a single stereo input that serves for both line/mic inputs - the mic signal gets routed into the line.  So you do pass a line signal through the mic amp, but for the most part it has no discernable impact on the sound.  Or I've never found it a problem.  I mean, does your mic pre cause your mic signal to suck?  Most pres today (even combo interface pres) are pretty clean, esp. when they don't need to add any gain to a line signal.  There are about a million other things for most home studios to worry about than the infinitesimal change a few circuits add to your signal when plugging a line into an interface pre. 

Oh I see now what you were saying about the 2i2 was what you had read about the pre amps, and that you actually do own the 6i6.. good.. problem solved.
Myself I see it as a mistake to purchase the 2i2 and the 2i4 over the 6i6. For not much more cash you get a heck of a lot more functionality and features. I can see using one for a mobile rig but not as my main interface.
 And for the same money you can get a Tascam us 2x2 which has better features and probably way better pre amps.
 But the Tascam is 2x the size so not very portable.