What tubes fro my el84 amp?

I recieved my first tube amp today and would like to know what others are using. It has a pair of 6cg7 drivers (rca) and the pwr tubes are russian (quad). The amp is actually a intergrated with only one input so I'm using my tube ASL pre for my other sources. My other question is what would make the greatest difference in sound the drivers or pwr tubes. At the moment I like what I hear but--- Stay thirsty my friends.
Thanks for your responses. I have a quad of JJ's on the way that are matched. I'll post my results once installed and burned in. Enjoy the music!
NOS Mullards are the gold standard with Tung Sols an excellent alternative.
Ghasley I did see some Mullards eleswhere and will keep them on the radar as well as Tung Sols. Thanks!
The JJ's arrived today and my smile is from ear to ear! These tubes are a keeper. Thanks to all.
Good to hear South. I had a Manley Stingray and rolled JJs in and thought they sounded very good.
Thanks for following up!