While I double-compress in a mix all the time, I would probably never do it while tracking. Its just too easy to accidentally overdo it(which can never be UNdone). I would go mic>preamp>compressor>interface. The KT2A would be my choice for vocals, but I might go with the 76 for some other sources
BUT**** the great big "but", since you never mention what interface, there is one more detail that matters. Make sure you go into the interface on a line level input and NOT a mic(XLR) input.
If you really feel compelled to go thru both compressors on the way in, I would take 2 signals(put up 2 audio tracks, make them a group, mute one, record both). 1 signal would be the output of the second compressor and the other signal would be the extra output of the first compressor(assuming they have both XLR and TRS outputs). This way, if you "overcook" with 2 comps, you also have a recording with only the first
