Flatest amp settings

[Dave2311]

Hi
Has anyone had any success in getting a signal that has a really flat response to use with a separate amp modeller? I've recently got hold of a Pod HD 500x and, as an fx modeller, it sounds great with my ID 60 using 4cm. But, It's amp modelling does not touch TVP. What I noticed Is that as well as the full amp, they have also just modelled the pre amp stage of each amp. What I want to do is use the pre amp stage in the pod and then use the IDs TVP power amp stage for valve emulation. As, there is no way to bypass the IDs preamp voice and eq and go straight to the TVP section, how do you think I'm best getting the least colour on my input and eq on the ID?
Thanks