Anyway I would suggest to use the excellent preamp-section of the Apollo, I always use my KPA analog, either straight into my channelstrip (DTC Dual Tube Channel) or straight into the Apollo inputs.
Here's a detailed information about the Twin, it's a very, very good interface.
Do you use/prefer XLRs or 1/4" from the Main Output into the Apollo Twin? Looking into a Apollo Twin.
Many thanks,