I think the VTF-2 mk4 is a better fit for some VTF-3 mk3s than two VTF-1s. The reason is tuning frequencies. The VTF-2 mk4 can be made to have more similar performance to the VTF-3 mk3s than the VTF-1s. Basically, it should be more comfortable at deep frequencies than the VTF-1s.