Best 6DJ8 for ARC SP11,mk11?

I recently purchased a near mint unit, primarily for the phono section. The unit has the original tubes, very extended,clean and quiet. ARC recommends their replacement tubes only. System could stand a little more tube warmth.
All opinions are welcome and apppreciated.
Check the identical posting several lines below
Excuse me but I didn't realize that the ARC SP11,mk11 and the SP9,mk11 were the same unit. I'm assume this is the post. Thanks, but I would like to hear comments from current owners.
If the originals are sovtech as I had in my arc I found a big improvement with amprex bugle boys and mullards both will give a warmer more natural tone. The mullard has a litle more treble extension. in my system(a little dark) I prefered the mullard.