I have been running a K-5xeMP and VX-5 twenty for one year. Then moved to a Rogue RP-7 for the headphone output. Both preamps played well with the VX-5.20. The K-5xeMP is my first pick when a "stock" comparison with the RP-7. the K-5xeMP has a very small advantage to the RP-7 in terms of "just right" sonics and has been considered a the best of tubes and solid state preamp for many years. The stock RP-7 has more connectivity (headphone, two XLR outs) and potentially could sound better with NOS or upgraded current production 12AU7 tubes. I loved the K-5xeMP and VX5.20. The RP-7 is current production and meets more of my daily requirements. I would live happily with either pairing.
