The two center positions will reveal a greater difference than the outer two. But, I suggest that power tube selection will have a far greater influence in the sound quality. If you haven't already done so, start there and then fine tune with the small tubes.
Primaluna - Rolling pre tubes question...
I'm new to rolling tubes, and have been using the stock 12AU7.
I've a PL Prologue premium integrated with 2 12AU7's per channel. I want to test a new pair(before investing in more), so wondering if front or rear position would best reveal the new tubes character?
Thanks,
Darren