best output tubes for jolida 502b

I just purchased a jolida 502b. This will be my second tube amp. I bought a sophia electric baby but it didnt go loud enough,(I like to rock out sometimes). Anyway the output tubes I got with the 502 are the stock ones and they have some hrs on them. Does anyone have any advice on what tube to use when I replace them.
I've always used NOS tubes, but when I wanted to replace the eight matched 6550s in my Cary mono-blocks, I almost went apoplectic! The prices have gone nuts on matched quads/octets of anything worth having(supply and demand strikes again). To my surprise and delight, The Winged "C" 6550's(St Petersburg plant) actually out-performed the Phillips octet that they replaced(more open and transparent). I wouldn't purchase output tubes from anyone but Upscale Audio. Their screening, and matching processes can't be beat! Kevin is anal about his quality control, and company's reputation(and I like that a lot). I have no other connection to them, other than as a very satisfied customer. Check out the test equipment/process descriptions he includes on his site:( Ask Kevin about KT88s in your application. You may be able to get a bit more output with them than with 6550s. Kevin will be able to advise you as to any differences in sonics between the two. Happy listening!!

I have the SED 'Winged C' KT88's in my AES Superamp and they are wonderful tubes. They're a different sound, which is what tube rolling is all about, but just as enjoyable to listen to as some of the more expensive NOS tubes I also have.
since the amp is new let the stock tubes stay in awhile to get used to the sound. my 502b came with stock eh 6550 and i later bought eh kt88. for the driver tubes i am using ge 6201 or mullard cv4024 in the 12at7 slots.
tungsol ecc803s in the 12ax7 slots. you can also sub 12au7 for 12ax7.
vintage tung one else close