+1 ARC SP9 vI, II or III depending on your budget. I just sold one that I used with a Threshold amp of similar vintage and, I suspect, sound profile to your P300. The combo sounded great with several Vandys and Thiels over the years.
SP9 has two tubes, one each in the line and phono stages so easy to roll if you decide to go down that rabbit hole ;)
SP9 has two tubes, one each in the line and phono stages so easy to roll if you decide to go down that rabbit hole ;)