I've tried Psvane T2's (KT88 and cv181z's) in my phi 200's and they were good, certainly better than the stock. I've played around with a number of combos - including and my favorite (so far) is GoldLion KT88's and NOS RCA 6SN7's (they have a gray color).
IMHO - the stock tubs are absolute rubbish.
IMHO - the stock tubs are absolute rubbish.