Tube rolling for my Luxman C38uc

[sidvee]

I rolled in a pair of mullard NOS 12au7 for the stock JJ's provided in the luxman. I could hear a bit more midrange warmth. Since I have only a pair of these tubes, which position would be the best to place them? You can see the quad set of tubes in the pic, which position in this would be the best for the pair?
Cheers,
Sid