Interconnects - better before preamp or after preamp?

There is no 'better' cable. Cables interact with the connected devices. The 'best' cable is the one that provides the listener with the most satisfying sound with the equipment they own.

I flat out guarantee that most AudioPhools who purchased cables by brand or other people's opinions have sub optimal sound.

There is no guarantee that any particular cable brand or style works best with any particular component. Add in the listeners' sonic preferences and all bets are off.

I've had 'critical' listeners with expensive HiFi systems tell me that my system has 'no bottom' and and another 'no sparkle' while those who know live music make comments like "Joe Pass is sitting right  T H E R E !!"

It's time correct with a slight downward drop from ≈25Hz to >22kHz - ala concert halls.