Line for both 
Yes, but with the Kemper you don't need to reamp through the instrument input. You can reamp thru its line inputs (return/alternative) by clicking the input button on your kemper and selecting "Input source" to be Return Input Reamp. The Ideal situation would be to use SPDIF for reamping but your interface doesn't have one.
In short, use line to record your wet and dry signals seperately, and if you want to reamp use the line output from your interface into the line input in the Kemper but you will have to change the Input Source on the kemper accordingly.
Don't forget to switch it back to "Front Input" when you are done 
Think of it this way: The kemper has a built in reamp box and a built in di box
Look in the reference manual - it's all there
Hi Jeremy,
Just to echo the comments of others in this thread - both the wet return from the Kemper and the DI will both be at line level (a standalone DI box takes an unbalanced instrument level signal and converts it to a balanced line/mic level signal) so you should set the 2i4 to 'Line'. Bear in mind that when connecting to the combi inputs on the front of the 2i4 you'll need to use a 1/4 inch jack connection rather than an XLR connection since an XLR connection will engage the mic preamp circuit rather than the Line/Inst circuit.
Best,
Jack // Focusrite Tech Support
