ask dave thomson at raven audio he also has a lot of NOS tubes for sale.
your phono amp may not be a good match for the integrated you have.
pass on mullard, brinar, amperex/philips and tungsram seem the wrong direction
for your qicksilver.
the raytehon iblack plate s worth a try.
if you want to spend a lot money, get mazda nickel plate; if you want to spend not as much, get telefunken smooth plate. RCA blackplate have good upper frequency extension as well
go ahead and start with the top dealer in the US, brnt jessee. hes not the cheapest but not the most expensive, neither. or check with dave thomson at raven audio hes welll-educated on the matter.