Cary SLI-80 Signature - Tube Recommendation


Hello Audiogoner - Please Advise/Help......THANKS....
Currently, I own a Cary SLI-80 Signature integrated amplifier and would like to try on a new/better tube. My price range is $50-$75 per tube. Please note this is a older model, it's about 6 years old.

1 - Rectifier Tube 5u4g (??????? I have no clue about this)

2 - Input Tube 6922 (I got Amperex white label, any other recommend ??????

3 - Power Tube 6550 - (Genalex Gold Lion KT88 tubes Valves 6550, any other recommend????????????

4 - Output Tube 6sn7gt - (??????? I have no clue about this)

Please help, I would like to hear from you for your recommendation............BIG THANKS.......

Joseph
xuandung
BIG THANKS to Mechans & Rodman99999
Pretty sure your comment is very help and interest on my research.............Thanks again......

Anyone out there has a good tip about rectifier 5u4g tube section on this Cary gear????????? NOS of RCA, Sylvania, Raytheon, Ken-Rad ????????Please advise.....THANKS...
Joseph
Mullard rectifiers have always given me the most enjoyable reproduction, and longest life(by far). ie: (http://cgi.ebay.co.uk/5U4G-VINTAGE-MULLARD-NOS-BROWN-BASE/310178367066)
Mullard 5U4G is a very nice choice. So are Tung Sol 5U4G Coke Bottles for a a lot less.